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Veterinary Parasitology 140 (2006) 204–216

Prevalence of Giardia and Cryptosporidium in dairy

calves in three areas of Norway

Inger Sofie Hamnes *, Bjørn Gjerde, Lucy Robertson

Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, Section of Microbiology,

Immunology and Parasitology, P.O. Box 8146 Dep, N-0033 Oslo, Norway

Received 24 August 2005; received in revised form 6 January 2006; accepted 22 March 2006

Abstract

A study was undertaken to determine the prevalences of Cryptosporidium and Giardia in dairy calves less than 6 months of

age in Norway. Faecal samples were collected from a total of 1386 calves, between 3 and 183 days of age, in 136 dairy farms

from three different areas of Norway. Faecal samples were examined for Cryptosporidium oocysts and Giardia cysts after

concentration and immunofluorescent staining.

Giardia was found in 93% (127 out of 136) of the farms and in 49% (679 out of 1386) of the calves. Cryptosporidium was

found in 53% (72 out of 136) of the farms and in 12% (167 out of 1386) of the calves. The level of Giardia and/or

Cryptosporidium was low in the majority of the infected calves.

Infection peaked in the age group 2–3 months for both Cryptosporidium and Giardia. The prevalences of both parasites were

higher in samples taken during winter than in samples taken during summer, and statistically significant differences were found

when prevalences in different age groups of calves were compared between the three areas. A significantly lower prevalence of

Cryptosporidium was found in calves housed in shared pens that were thoroughly washed more than three times a year than in

calves from pens washed less often. For Giardia there was a trend for decreasing intensity of infection with increasing age in the

sampled calves. For Cryptosporidium there was a trend for increasing herd prevalence with increasing number of calves in the

herd, but this trend was not statistically significant. Other parameters which were investigated such as housing, feeding or

management routines were not associated with prevalence or intensity of infection with either parasite.

# 2006 Elsevier B.V. All rights reserved.

Keywords: Cryptosporidium; Giardia; Cattle; Prevalence; Calves; Norway

* Corresponding author. Tel.: +47 22 96 49 69;

fax: +47 22 96 49 65.

E-mail address: inger.hamnes@veths.no (I.S. Hamnes).

0304-4017/$ – see front matter # 2006 Elsevier B.V. All rights reserved

doi:10.1016/j.vetpar.2006.03.024

1. Introduction

Members of the genera Giardia and Cryptospor-

idium are commonly identified intestinal protozoan

parasites of mammals including humans. Giardia and

Cryptosporidium have emerged as important parasites

.

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 205

of dairy cattle because of their proven pathogenicity,

and the potential public health significance of zoonotic

transmission (Olson et al., 2004). Cryptosporidium

infections are common in humans and calves, and also

occur in dogs, cats, pigs, horses, sheep, goats and

wildlife (Fayer, 2004). Giardia infections are common

in humans and domesticated animals, especially

livestock, but also occur in dogs, cats and numerous

species of wild mammals and birds (Thompson,

2004). Both Cryptosporidium oocysts and Giardia

cysts are infective at the time they are excreted from

the host and the cysts/oocysts are environmentally

robust and can survive for long periods outside the

host, particularly in moist environments (Olson et al.,

2004).

Infected calves can excrete large numbers of cysts/

oocysts, up to 108 per gram of faeces (Uga et al.,

2000). Transmission from one host to another is

achieved by ingestion of oocysts for Cryptosporidium

or cysts for Giardia. Transmission can be direct from

host to host, or by ingestion of faecally contaminated

food or water. As with other faecally transmitted

parasites, mechanical insect vectors are likely to play a

role in transmission (Graczyk et al., 2003).

A number of North American and European studies

have shown both parasites to be highly prevalent in

dairy calves with infection rates as high as 100% in

some herds, and have also demonstrated an association

between parasite infection and diarrhoea and significant

production losses (de Graaf et al., 1999; O’Handley

et al., 1999, 2001; Huetink et al., 2001; Olson et al.,

1995, 2004). Giardiasis in domestic ruminants has a

negative effect on performance, resulting in decreased

rate of weight gain, impaired feed efficiency, lower

carcass weight and increased time to slaughter (Olson

et al., 1995, 2004). Cryptosporidium infections in

calves can cause diarrhoea, and calves can become

lethargic, anorectic and dehydrated. Calves with severe

cryptosporidiosis can take 4–6 weeks to recover fully

(Olson et al., 2004), and economic losses due to

cryptosporidial infections are related to diarrhoea and

the extra costs special care of diarrhoeic calves demand

(de Graaf et al., 1999).

The genus Giardia currently comprises six species,

of which Giardia duodenalis (syn. G. intestinalis, G.

lamblia) infects humans as well as other mammals

(Monis and Thompson, 2003). G. duodenalis can be

considered as a species complex with at least seven

distinct genotypes or Assemblages based on genetical

analysis. Only G. duodenalis of Assemblages A and B

have been found in humans, as well as in a wide range

of other mammalian hosts (Lalle et al., 2005).

Cattle are susceptible to infection with three

genotypes of G. duodenalis, the zoonotic genotypes

of Assemblages A and B (Lalle et al., 2005), and the

hoofed livestock genotype of Assemblage E (Thomp-

son, 2004). Although the livestock genotype appears

to occur more frequently in cattle than the other two,

the occurrence of the zoonotic genotypes (Assem-

blages A and B) is of potential public health

significance. In a study of Canadian and Australian

calves a total of 17% (3 of 18) of the calf isolates of

Giardia from both countries were of the zoonotic

genotype Assemblage A (O’Handley et al., 2000).

Currently there are 14 commonly accepted species

of Cryptosporidium (Xiao et al., 2004; Caccio et al.,

2005; Fayer et al., 2005), six of which have been found

to be infective for cattle. Cattle are commonly infected

by Cryptosporidium parvum and C. bovis in the

intestine, and C. andersoni in the abomasum. But C.

felis infections have also been reported from this host.

Cattle have also been experimentally infected with C.

canis and C. hominis (Xiao et al., 2004).

C. parvum of cattle also infects other mammals,

including humans, whereas C. andersoni seems to be

confined to cattle, Bactrian camels and sheep. C. bovis

infect sheep in addition to cattle (Fayer et al., 2005).

There is evidence of human cryptosporidiosis being

associated with farms and exposure to infected

livestock, particularly young cattle, animal manure

and contaminated water. Grazing farm animals (cattle,

sheep, and goats) and wild cervids and other wildlife

might be a potential source of Giardia cysts and

Cryptosporidium oocysts in water sources.

Genotyping of Cryptosporidium infections in

humans has revealed some interesting differences

between the situation in Australia and North America,

where most cases are of human origin, and in Europe

where zoonotic sources of infection appear to be more

common (Joachim, 2004). In immunocompetent

humans C. parvum usually causes a self-limiting

disease, but in the immunocompromised host it may

cause severe disease, and such hosts often are unable

to rid themselves of the infection (Joachim, 2004).

In Norway there is little knowledge about the

prevalences and significance of Cryptosporidium and

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216206

Giardia in domestic animals, wildlife and humans. A

survey by Nygard et al. (2003) showed that Norwegian

medical microbiology laboratories rarely screen for

Cryptosporidium. The Parasitology laboratory at the

Norwegian School of Veterinary Science has spor-

adically diagnosed both Cryptosporidium and Giardia

from several domestic species. Studies have shown

Giardia and Cryptosporidium to be rather prevalent in

Norwegian water sources (Robertson and Gjerde,

2001). Previously no studies have been carried out on

the prevalences of these two parasites in cattle in

Norway. In light of the clinical importance, causation

of production losses and zoonotical potential of both

Cryptosporidium and Giardia infections, more knowl-

edge about the prevalences of the parasites was

needed. The aim of this study was to obtain data about

the prevalence of these two parasites in Norwegian

cattle, primarily in calves and young animals.

1 Kukontrollen: voluntary health and production recording system

for dairy herds, in which 95% of Norwegian dairy herds are

registered.

2. Materials and methods

2.1. Area description

Cattle from three areas of Norway were included in

the study (Fig. 1).

The first area was Jæren in Rogaland County, on the

west coast, consisting of three municipalities: Ha,

Klepp and Time. This area is characterized by high

farm animal density, moist, mild coastal climate and

large farms. Calving occurs throughout the year, but

peaks slightly in March, April and August. The

average numbers of dairy cows at the selected farms

was 21.8. The average rainfall per year in these

districts was 1310 mm, the average temperature in

January and July was 0.6 and 14.0 8C, respectively.

The second area was in Nord-Trøndelag County in

Mid-Norway, and consisted of four municipalities:

Inderøy, Levanger, Steinkjer and Verdal. This area is

characterized by medium to high animal density,

medium sized farms (average number of dairy cows at

each farm in this district was 16.6), a coastal climate,

but with colder winters than in Jæren. Calving occurs

throughout the year, but peaks slightly in the months

between May and August. The average rainfall per

year in these districts was 893 mm, and the average

temperature in January and July was �3.6 and

14.0 8C, respectively.

The third area was Valdres in Oppland County,

consisting of six municipalities: Øystre Slidre, Vestre

Slidre, Nord-Aurdal, Sør-Aurdal, Etnedal and Vang.

This area is characterized by an inland climate, dry

cold winters, low farm animal density and rather

small farms (average number of dairy cows at each

farm was 12.5). Calving occurs throughout the year,

but peaks from September to December (following

the grazing season). The average rainfall per year in

these districts was 632 mm, and the average

temperature in January and July was �10.5 and

14.5 8C, respectively (see Table 1 and Fig. 2).

2.2. Selection of farms

Only dairy farms were included in the study. A list

of dairy farmers in the selected districts in year 2000

was obtained from Kukontrollen1 in Norway. Farms

with less than 5 cows or more than 40 cows were

excluded. The remaining farms in each area were

allocated a random number and sorted according to

these numbers. Starting at the top of each list the

farmers were contacted by mail and asked to

participate in the study. The farmers were then

contacted by phone, confirming participation, and if

not, excluded. Each farm that was excluded was

replaced by the next farm on the list. In each area,

farms were included until a minimum of 450 adequate

faecal samples had been obtained.

2.3. Sample collection

Samples were collected between June 2001 and

March 2003. All calves sampled in this study were

housed inside.

Faecal samples were collected from the rectum of

each calf using a disposable latex glove. The glove was

tied off and marked with the calf’s individual number

and placed in a zip-bag together with the other samples

from the same herd. Samples were taken from all

available calves between 3 and 183 days of age in the

selected herds. Samples were kept cold until

laboratory examinations took place. The samples

from Nord-Trøndelag and Rogaland County were

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 207

Fig. 1. Map of counties of Norway (Map of Norway, sampled counties shaded with grey).

Table 1

Data on herds, calves and time of sampling

Area No. of herds

examined

No. of

samples

Mean no. of

calves (range)

Mean age

calves (day)

Sampling period

Rog 32 450 14 (2–34) 95 Summer, fall 2001, winter 2002

Opp 47 475 10 (3–25) 101 December 2002, March 2003

N-T 57 461 8 (1–21) 77 Summer, fall 2001, winter 2002

Total 136 1386 11 91

Rog: Rogaland County, Opp: Oppland County, N-T: Nord-Trøndelag County.

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216208

Fig. 2. Distribution of calves in different age groups from each area. Rog: Rogaland County; Opp: Oppland County; N-T: Nord-Trøndelag.

shipped by mail to the laboratory in Oslo, those from

Oppland were brought in by the investigator. For each

herd sampled, a questionnaire was completed by the

owner at the time of sampling. In this questionnaire

information about herd size, housing system (move-

ment of cows restricted or not), housing (shared or

common pens, for calves of different age groups),

feeding, and cleaning routines for the calves, presence

of other farm animals, and presence of gastro-

intestinal illness among the calves over the past year

was recorded. Information about each calf (such as

ear-tag number, age, sex, housing (single pen, shared

pen or fixed), faecal consistency and prevalence of

diarrhoea during the last 14 days before sampling) was

recorded by the investigator in a ‘‘Registration form

for calves’’. A total of 1386 samples suitable for

analysis were collected, 994 samples during the winter

(October–March), and 992 during the summer (April–

September). Samples that contained too little material,

or came from farms that subsequently did not fulfil the

inclusion criteria, were excluded from the study and,

and in the latter case, replaced by new samples.

2.4. Sample analysis

The samples were analyzed by a sucrose flotation

method as described by Olson et al. (1997a). Briefly,

approximately 3 g of faeces (mean weight = 2.7 g)

was suspended in approximately 10 ml of PBS

(phosphate buffered saline) and mixed to a homo-

genous suspension. The suspension was then filtered

through a surgical gauze sponge (Compresses de gaze,

Bastos Viegas s.a., Penafiel, Portugal) using manual

pressure to yield approximately 7 ml of filtrate. The

filtrate was layered on top of 5 ml of 1 M sucrose for

clarification. The sample was then centrifuged at

800 � g for 5 min to concentrate the cysts/oocysts.

The interface and the upper layer of liquid were

transferred by pipette to a clean tube and recentrifuged

(800 � g; 5 min). The supernatant was decanted and

the pellet resuspended in PBS to a volume of 1 ml.

Thirty microliters volumes were air-dried to

microscope slides, methanol fixed and stained with

fluorescein-labeled (FITC) monoclonal antibody

against oocysts of C. parvum, and Cy-3-labeled

monoclonal antibody against cysts of G. lamblia (A

100FR FL/CY3 from Waterborne Inc., New Orleans,

USA). After incubation, excess antibody was washed

off with PBS and the slide left to air dry before

mounting (DABCO/glycerol mounting medium 2%)

with a 22 mm2 cover slip. The area under the cover slip

was examined using an epifluorescent microscope

(Leica DMBL) at 200� and 400� magnification,

using an I3 and an N2.1 filter respectively, when

viewing for Cryptosporidium and Giardia. With each

batch of stained slides, a known positive sample for

both parasites was stained and used as a control. This

procedure has a theoretical detection limit of 10 cysts/

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 209

oocysts per gram of faeces if 3 g of faecal sample is

used and the resuspended pellet volume is 1 ml.

Samples were classified as negative (no cysts/oocysts

found), as 1+ if 1–5 cysts/oocysts, as 2+ if 6–10 cysts/

oocysts, or as 3+ if >10 cysts/oocysts could be found

on average in each of 20 fields of view at 400�magnification, respectively. A herd was considered

positive if one or more of the calves had Cryptospor-

idium and/or Giardia. Measurements of cysts/oocysts

were made using a calibrated eyepiece graticule.

2.5. Statistical analysis

Statistical analyses of the data were performed using

MS Excel Spread Sheet for Windows (Office 2003

version), JMP, The Statistical Discovery Software,

version 5.0.1.a, from SAS Institute Inc. and QuickCalcs

from GraphPad SoftwareInc, using Fisher’s exact test,

x2 test and t-test. Parameters investigated with regard to

the prevalence of Giardia and Cryptosporidium were:

herd size, housing of calves less than 3-weeks old and

calves older than 3 weeks, and housing of the individual

calves at sampling time, feeding routines for the same

two age groups, use of bedding, cleaning and washing

routines of individual/shared pens, occurrence of

Table 2

Herd prevalence and overall prevalence with 95% confidence intervals

Area

Rogaland O

Cryptosporidium

No. of positive herds (%) 21 (65.6)

95% CI (%) 48.4–70.8

No of positive calves (%) 71 (15.8)

95% CI (%) 12.7–19.5

Giardia

No. of positive herds 31 (96.9)

95% CI (%) 8.31 to >99.9

No. of positive calves 210 (46.7) 2

95% CI (%) 42.1–51.3

Cryptosporidium and Giardia

No. of positive herds b 21 (65.6)

95% CI (%) 48.4–79.8

No. of positive calves c 41 (9.1)

95% CI (%) 6.8–12.2

a The prevalence in Nord-Trøndelag was statistically significant differb No. of positive on average herds: herds with both Giardia and Cryp

calves).c No. of positive calves: calves with both Giardia and Cryptosporidiu

gastrointestinal disease among the calves in the herd

during the year previous to sampling, faecal consistency

at sampling, occurrence of diarrhoea in sampled

animals during the last 14 days before sampling,

overall and herd prevalences of the parasites between

seasons, areas, intensity of infection compared to age of

calves, and dual infections.

3. Results

Results are summarized in Tables 2–5.

Cryptosporidium negative and positive herds had a

mean of 8 (1–21) and 12 (3–34) calves sampled,

respectively. Giardia negative and positive herds had a

mean of 6 (2–19) and 11 (1–34) calves sampled,

respectively. None of the 80 samples from calves

younger than 15 days tested positive for Cryptospor-

idium, and only 4 of the 121 calves younger than 3

weeks tested positive for Cryptosporidium. None of

the herds sampled had more than five calves under the

age of 22 days at sampling time. Herd prevalences by

county are given in Table 2. Prevalence of Giardia in

samples taken during the winter and summer were

56% and 42%, respectively. Prevalence of Cryptos-

ppland Nord-Trøndelag Total

29 (61.7) 22 (38.6)a 72 (59.9)

47.5–74.3 27.1–51.7 44.3–61.2

57 (12.0) 39 (8.5) 167 (12.0)

9.8–14.8 6.6–10.9 10.4–13.9

44 (93.6) 52 (91.2) 127 (93.4)

82.3–98.7 80.7–96.7 87.8–96.7

64 (55.6) 205 (44.5) 679 (49.0)

51.1–60.0 40.0–49.0 46.4–51.6

29 (61.7) 21 (36.8) 71 (52.2)

47.5–74.3 25.6–49.9 43.9–60.5

29 (6.1) 27 (5.8) 97 (6.9)

4.3–8.7 4.0–8.4 5.8–8.5

ent from prevalences in Rogaland and Oppland.

tosporidium diagnosed (not necessarily dual infections in the same

m diagnosed (dual infections).

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216210

Table 3

Frequency of faecal samples with different numbers of cysts/oocysts

Categorya Mean calf age

Cryptosporidium Giardia

Neg 1219 (91 days) 707 (99 days)b

1+ 153 (92 days) 587 (97 days)

2+ 13 (78 days) 54 (67 days)

3+ 1 (80 days) 38 (65 days)

a Neg: no cysts/oocysts found. 1+: 1–5 cysts/oocysts on average

in each of 20 fields of view; 2+: 6–10 cysts/oocysts on average in

each of 20 fields; 3+:>10 cysts/oocysts found on average in each of

20 fields at 400� magnification.b The calves in the Giardia negative group had a statistically

significant higher mean age than the calves of the three Giardia

positive groups.

poridium in samples taken during the winter and

summer were 16% and 8%, respectively.

The majority of the positive samples contained

only a few cysts/oocysts (Table 3). The size,

morphology and morphometry of all the oocysts were

consistent with those described for C. parvum, but C.

felis and C. bovis could not be excluded. None had the

appearance of oocysts of C. andersoni.

Out of 129 calves with Cryptosporidium infection,

97 also had Giardia infection (76%), whereas among

Cryptosporidium negative calves, only 46% had

Giardia.

On a herd level, 1 out of 9 (11%) of the Giardia

negative herds had Cryptosporidium, whereas 71 out

of 127 (56%) of the Giardia positive herds also had

Cryptosporidium.

Statistical analysis that yielded significant differ-

ences is shown in Table 5.

Seasonality and geography. Overall prevalence of

Giardia and of Cryptosporidium was higher in

Table 4

Age-related prevalence of Cryptosporidium and Giardia

Age group (day) Prevalence of Cryptosporidium (%)

Rog Opp N-T Overall in g

3–31 3.9 15.2 a 4.9 a 7.0

32–61 13.5 14.6 9.4 12.0

62–92 21.4 17.5 13.4 17.3

93–122 22.5 12.1 9.1 14.9

123–153 18.1 b 7.9 3.6 b 11.2

154–183 6.0 6.7 3.1 7.1

For each parasite and age group prevalences marked with the same letter (a

County, Opp: Oppland County, N-T: Nord-Trøndelag County.

samples taken during winter than in samples taken

during summer for both parasites. In the two counties

which had sampling both in winter and summer

(Rogaland and Nord-Trøndelag) statistically signifi-

cant lower prevalences of both Cryptosporidium and

Giardia in summer than in winter were found in both

counties. Samples taken during summer showed

statistically significant lower prevalence of both

Cryptosporidium and Giardia than samples taken in

the other quarters of the year (Table 5). The prevalence

of Giardia in Oppland was not statistically signifi-

cantly different from the prevalences of Giardia in

Rogaland and Nord-Trøndelag in the same season.

There was a higher prevalence of Cryptosporidium in

samples taken in July in Rogaland than in Nord-

Trøndelag but no such difference for samples taken in

January and August in these two counties.

Feeding and housing routines. There was a lower

prevalence of Giardia in calves older than 3 weeks

from farms that fed calves individually as compared to

farms that used shared feeding. There was a

statistically significant lower prevalence of Cryptos-

poridium in calves housed in shared pens that were

thoroughly washed three or more times a year as

compared to pens washed with lower frequencies.

Herd size. There appeared to be a trend towards an

increase in Cryptosporidium herd prevalence with

increasing number of calves in the herds at sampling,

but this was not statistically significant. None of the

other parameters investigated, with regard to housing,

feeding or management routines, occurrence of

diarrhoea during the last 14 days before sampling

or gastrointestinal disease among the calves over the

past year demonstrated statistically significant differ-

ences.

Prevalence of Giardia (%)

roup Rog Opp N-T Overall in group

38.5 37.8 24.5 30.5

54.1 57.8 52.1 54.3

52.8 61.2 58.8 57.8

56.3 65.1 c 43.9 c 55.9

40.0 52.8 d 33.9 d 43.2

32.0 ef 52.2 f 56.8 f 47.8

,b,c,d,e,f) are statistically different from each other. Rog: Rogaland

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 211

Table 5

Variables examined, statistical test performed and P-values

Variable Detail Statistical test

performed

P value

Cryptosporidium Giardia

Geography Overall prevalence

N-T–Rog x2 test 0.0007 >0.05

N-T–Opp x2 test >0.05 0.0007

Ro–Opp x2 test >0.05 0.0067

Herd level prevalence

N-T–Rog Fisher’s 0.0143 >0.05

N-T–Opp Fisher’s 0.0190 >0.05

Rog–Opp Fisher’s >0.05 >0.05

Seasonality Area–season

Overall: winter–summer x2 test <0.0001 <0.0001

Rogaland: winter–summer x2 test <0.0001 0.0099

Nord-Trøndelag: winter–summer x2 test 0.0092 0.0014

Oppland: December–March x2 test 0.0460 >0.05

Quarterly

June–August–December–February x2 test <0.0001 <0.0001

June–August–March–May x2 test 0.0057 <0.0001

June–August–September–October x2 test 0.0254 <0.0001

Agea Overall prevalences in different age

group—in different counties

3–31 days: Opp–N-T Fisher’s 0.0334 >0.05

93–122 days: Opp–N-T x2 test >0.05 0.0099

123–153 days: Rog–N-T x2 test 0.0427 >0.05

Opp–N-T x2 test >0.05 0.0262

154–183 days: Rog–Opp x2 test >0.05 0.0212

Rog–N-T x2 test >0.05 0.0155

Intensity of infection Mean age of calves in different intensity

of infection categories

Neg–1+ t-Test >0.05 0.0032

Neg–2+ t-Test >0.05 0.0288

Neg–3+ t-Test >0.05 0.0064

1+ to 2+, 1+ to 3+, 2+ to 3+ t-Test >0.05 >0.05

Feeding routines Calves older than 3 weeks

Individual feeding–shared feeding Fisher’s >0.05 0.0030

Herd sizeb Herd prevalence – number of

calves sampled (from each herd) –

different size groupc

x2 test/Fisher’s >0.05 >0.05

Occurence of diahrroea Diarrhoea during last 14 days before sampling Fisher’s >0.05 >0.05

GI disease in calves in herd last 12 months—or not Fisher’s >0.05 >0.05

Housing/cleaning

routines (calves)

Calves in shared pens Thoroughly

washed �3 times a year—pens washed

with lower frequencies

x2 test <0.0001 >0.05

Faecal consistency at sampling Diarrhetic–normal Fisher’s >0.05 >0.05

a Only the comparisons which yielded statistical significant differences are listed in this table. See also Table 4.b Number of calves.c Size groups: 1–5 calves, 6–10 calves, 11–15 calves, 16–20 calves, 21–34 calves (there were few herds with more than 20 calves, so these

have been included in one group (21–34)).

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216212

4. Discussion

The results of this study demonstrate that

Cryptosporidium and Giardia are prevalent in calves

and young cattle in Norway, as also found in numerous

similar studies in other countries (Table 6).

The current study shows the overall prevalence

among calves to be 12% and the herd prevalence to be

53% for Cryptosporidium. For Giardia the overall

prevalence was 49% and the herd prevalence was

93%. Point prevalence and herd prevalence data are

influenced by a range of factors including analytical

Table 6

Selected studies on prevalences of Cryptosporidium and Giardia in calve

Age group (number

of calves sampled)

Country % Prevalence

Cryptosporidium Giardia

0–17 weeks (7369) USA 48.1a/21.9b/<15c n.e.

�4 months (554) Spain 14–53.8 14.1–38

�6 months (25) Canada 15 73

�6 months (386) Canada 15 31

2–16 weeks Canada n.s. n.s.

4–12-days old (1628) France 17.9d

4–21-days old (440) 43.4e

20–10 weeks (28, 36) Canada, Australia n.e. 57, 58

5 days–2 months (503) USA 50.3 (4.7–78.3)f n.e.

3–11 months (468) USA 19.7 (2.9–66.7)f n.e.

�1 month (30) Japan 93 n.e.

Calves USA 22 n.e.

Europe 6–92

Asia 11–15

Other areas 25–59

�6 months (1135) USA 2.4 20.1

�4 months (112) The Netherlands 16.7–42.1 <1 to 2

�48 months (628) The Netherlands 8.6 0–54.5g

�6 months (n.s.) Germany 20–30 n.e.

�25–28 weeks (20) Canada 5h 100h

�8 weeks (639) UK 12.9–52i n.e.

<7 weeks (513) USA n.e. 44j

3–11 months (464) USA n.e. 31j (0–6

n.s.: not stated; n.e.: not examine.a 1–3-weeks old.b 3–5-weeks old.c >5-weeks old.d Survey 1.e Survey 2.f In the different herds in the study.g In different age groups.h Cumulative infection rates per herd.i Annual prevalences for 6 years.j By IFA.

method and study design, geographical differences,

age composition of sampled calves, number of

samples from each farm, total number of samples,

herd size and sampling season. Therefore, some

degree of variation should be expected between

studies that differ in one or more of these parameters.

Sturdee et al. (2003) showed that there are substantial

differences in prevalence of Cryptosporidium

between different years and between seasons, which

illustrates the dangers of basing assessments on single

years, or on parts of years, because the variations can

be large. Therefore, ‘‘snapshots’’ representing short

s up to 11 months of age

Herd level % prevalence Reference

Cryptosporidium Giardia

59.1 (652/1103) n.e. Garber et al. (1994)

63.3 (19/30) 53.3 (16/30) Quılez et al. (1996)

80 (16/20) 100 (20/20) Olson et al. (1997a)

100 (6/6) 100 (6/6) Olson et al. (1997b)

88.7 (448/505) 45.7 (231/505) Ruest et al. (1998)

Lefay et al. (2000)

55.6e (105/189)

n.e. (1/1), (2/2) O’Handley et al. (2000)

100 (14/14) n.e. Santın et al. (2004)

100 (14/14) n.e. Santın et al. (2004)

(1/1) n.e. Uga et al. (2000)

n.s. n.e. As referred by

Uga et al. (2000)

13 (14/109) 70 (76/109) Wade et al. (2000a)

0 (1/1) (1/1) Huetink et al. (2001)

(1/1) (1/1) Huetink et al. (2001)

n.s. n.e. Joachim et al. (2003)

(1/1) (1/1) Ralston et al. (2003)

(1/1) n.e. Sturdee et al. (2003)

n.e. 100j (14/14) Trout et al. (2004)

7)g 93j (13/14) Trout et al. (2005)

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 213

time spans may not be representative of the general

situation.

Norwegian dairy farms are small compared to

farms in most other studies concerned with Cryptos-

poridium and Giardia prevalences. In 2004 the

average number of cows in a Norwegian dairy herd

was 16.6 cows. Since dairy farms often have calving

dispersed throughout the year, the number of young

and susceptible animals at a typical Norwegian farm at

any given time is generally low. Garber et al. (1994)

demonstrated a relationship between the number of

samples collected per farm and the probability of the

herd testing positive for Cryptosporidium. Small

farms were less likely to test positive than large

herds even if the same number of calves were tested.

Because only one faecal sample was collected from

each animal in the present study, it is likely that the

point prevalence herein underestimates the actual

numbers of infected animals both for Cryptosporidium

and Giardia.

Negative classification of herds (for both categories

of parasites) could result from at least four different

scenarios: a truly negative herd, too few calves tested

to detect infection, infected calves not shedding cysts/

oocysts or shedding below the detection threshold at

sampling, or that the tested calves had recovered from

earlier infection(s) and did not shed at sampling time.

Various studies have shown the cumulative pre-

valences for both parasites to be 100%, and a number

of studies have shown a wide range in prevalence of

Cryptosporidium, from 6.2% to close to 100% and

herd level prevalences from 13% to 100% (Table 6).

The prevalences in this study are towards the lower

end of the scale as compared to other investigations.

Giardia infections have been reported frequently in

calves. Point prevalence studies often report widely

varying levels of infection, 1–100% (Xiao, 1994),

while the cumulative prevalence for a given farm often

reaches 100% (Xiao and Herd, 1994; O’Handley et al.,

1999).

In the current study the prevalence of Giardia was

>30% in all age groups, but with the highest

prevalence of Giardia infection in calves between

3-and 4-months old. This is in accordance with the

findings of Olson et al. (1997a) and Trout et al. (2005)

who found the highest prevalences of Giardia in

calves aged about 3 months. Different studies have

shown the peak prevalence of Giardia to vary from

around 4 weeks to 4–5 months of age (O’Handley

et al., 1999; Huetink et al., 2001; Becher et al., 2004).

In this study, the intensity of infection appeared to

decline with age. Statistical analysis showed this to be

true for Giardia, but for Cryptosporidium the trend

was not statistically significant. For Giardia there are

statistically significant differences between mean calf

age for the negative group and all three positive

groups. This trend is consistent with the infection

dynamics of both parasites in cattle, where the age of

peak shedding is 5 weeks and with a duration of

shedding of >30 weeks for Giardia, and peak

shedding at 1–2 weeks of age for C. parvum, with a

duration of shedding of 1–2 weeks (Olson et al., 2004).

Huetink et al. (2001) found the highest oocyst/cyst

counts in animals between 9- and 29-days old for

Cryptosporidium, and between 1- and 8.4-months old,

with an average of 3.7 months for Giardia, whereas

Olson et al. (1997a) found the highest counts in

animals between 2 and 4 weeks for Giardia and 0 and

2 weeks for Cryptosporidium. The calves in this study

with the highest intensity of Cryptosporidium infec-

tion had a higher average age than that reported

elsewhere; this is probably associated with the peak

prevalence of Cryptosporidium in this study occurring

at a later age than has been found in other studies.

When comparing prevalences from the three

different areas it must be taken into consideration

that most samples from Nord-Trøndelag and Rogaland

were collected during summer, whereas all of the

samples from Oppland were collected during winter.

There are significant differences in prevalences in

samples collected in the different seasons (Table 5)

and therefore the high prevalence of Giardia noted in

Oppland compared to the two other counties might be

an artifact of sampling season rather than geographical

differences in prevalence. However, samples taken in

July (in Rogaland and Nord-Trøndelag) show a

significantly higher prevalence of Cryptosporidium

in Rogaland than in Nord-Trøndelag. Nord-Trøndelag

had the lowest herd prevalence of both parasites and

the lowest overall prevalence for both parasites,

despite the fact that Nord-Trøndelag had the youngest

calves (mean age 77 days) sampled in this study, but

with fewest calves on each farm (average eight

sampled calves per farm). Rogaland had the highest

herd prevalence and most calves per farm (average 14

per farm). Some studies have shown that with higher

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216214

animal density, more animals become infected

(Garber et al., 1994; Mohammed et al., 1999), but

other studies have shown the opposite (Castro-

Hermida et al., 2002). The data in the current study

show a similar trend for Cryptoporidium, but this trend

is not statistically significant. Oppland is in between

the two other areas with respect to herd prevalence and

number of calves sampled per farm, but had the oldest

calves (average 101-days old) and the highest overall

prevalence of Giardia. This is consistent with the

accepted premise that Giardia is more prevalent

among older calves than Cryptosporidium.

Several studies have shown that there could be

substantial differences in the prevalence of Cryptos-

poridium during different seasons. Some studies

report an association between high seasonal preva-

lence and/or oocyst shedding intensities with peak

periods for newborn calves (Garber et al., 1994; Xiao

and Herd, 1994; Mohammed et al., 1999; Sturdee

et al., 2003). In the current study both parasites had

significantly higher prevalences in winter than in

summer. This is in accordance with a French study by

Lefay et al. (2000) who found that the lowest levels of

Cryptosporidium were found in samples taken in July

and August, but is in contrast with Garber et al. (1994)

and Wade et al. (2000a) who found that animals were

at higher risk of infection in summer than in winter.

Huetink et al. (2001) found highest levels of

Cryptosporidium in October, December and June,

while Sturdee et al. (2003) found the highest

prevalences in autumn. Wade et al. (2000a) found

that calves were at higher risk of becoming infected

with Giardia in summer than in winter, while Huetink

et al. (2001) found highest levels of Giardia in

December and February. The higher prevalence in

winter in this study could be explained by a number of

factors including higher number of animals indoors, as

the animals are kept indoors from late autumn to early

summer, and this gives a more crowded environment;

seasonal calving (in Oppland County there is a greater

tendency towards seasonal calving than in the other

two areas, and many calves are born in September and

October following the grazing season), which results

in a higher number of susceptible animals housed

together. Post-weaned calves and heifers are usually

on pasture during the summer months; therefore their

environment is less crowded for the youngest calves

that are kept inside. Summer is also the time of year

when it is most convenient to clean the housing, since

post-weaned calves, heifers and the cows are mostly

on pasture. Thorough cleaning and low density of

animals will reduce the level of cysts/oocysts in the

environment. Crowding during the winter months may

reduce the possibility for optimal cleaning routines

resulting in a heavier pathogen load in the environ-

ment. Crowding also increases contact between

animals, increasing the possibility of direct transfer

of pathogens from one animal to another. Moreover,

oocysts and cysts survive longer at moderate

temperatures than at higher temperatures.

Some studies have not found any seasonal

difference in the prevalence of Cryptosporidium and

Giardia (Ongerth and Stibbs, 1989; Wade et al.,

2000b; Castro-Hermida et al., 2002; Starkey et al.,

2005), which may be attributed to differences in the

study population, design or geographical location.

5. Conclusion

This is the first systematic study of the prevalence

Cryptosporidium and Giardia in Norwegian cattle and

demonstrates that, as found in many other countries,

these parasites are relatively widespread, with over

50% of the herds demonstrating infection with

Cryptosporidium and over 90% of the herds demon-

strating infection with Giardia.

Since C. parvum from cattle can infect humans, and

since some cattle can harbour G. duodenalis of the

zoonotic genotypes of Assemblages A and B, further

studies with genotyping of isolates of the parasites

from Norwegian cattle are necessary to evaluate their

public health significance and may also give further

insights into the epidemiology of these infections and

their importance to cattle in Norway.

Acknowledgements

The authors wish to thank all the farmers who

participated in this study and the veterinary students

(Marit Gundersen Skjærvik and Knut Undheim) and

the technicians (Asbjørg Husdal, Lene Hermansen)

involved in the sample collection and processing,

respectively. The authors also wish to thank Jorun Jarp

at the National Veterinary Institute for help with

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216 215

planning of study design. This study was partly funded

by a grant from The Norwegian Research Council.

References

Becher, K.A., Robertson, I.D., Fraser, D.M., Palmer, D.G., Thomp-

son, R.C.A., 2004. Molecular epidemiology of Giardia and

Cryptosporidium infections in dairy calves originating from

three sources in Western Australia. Vet. Parasitol. 123, 1–9.

Caccio, S.M., Thompson, R.C.A., McLauchlin, J., Smith, H.V.,

2005. Unravelling Cryptosporidium and Giardia epidemiology.

Trends Parasitol. 21, 430–437.

Castro-Hermida, J.A., Gonzalez-Losada, Y.A., Ares-Mazas, E.,

2002. Prevalence of and risk factors involved in the spread of

neonatal bovine cryptosporidiosis in Galicia (NW Spain). Vet.

Parasitol. 106, 1–10.

de Graaf, D.C., Vanopdenbosch, E., Ortega-Mora, L.M., Abbassi,

H., Peeters, J.E., 1999. A review of the importance of cryptos-

poridiosis in farm animals. Int. J. Parasitol. 29, 1269–1287.

Fayer, R., Santın, M., Xiao, L., 2005. Cryptosporidium bovis N. sp.

(Apicomplexa: Cryptosporididiidae) in cattle (Bos taurus). J.

Parasitol. 91, 624–629.

Fayer, R., 2004. Cryptosporidium: a water-borne zoonotic parasite.

Vet. Parasitol. 126, 37–56.

Garber, L.P., Salman, M.D., Hurd, H.S., Keefe, T., Schlater, J.L.,

1994. Potential risk factors for Cryptosporidium infection in

dairy calves. J. Am. Vet. Assoc. 205, 86–91.

Graczyk, T.K., et al., 2003. Detection of Cryptosporidium parvum

and Giardia lamblia carried by synanthropic flies by combined

fluorescent in situ hybridization and a monoclonal antibody. Am.

J. Trop. Med. Hyg. 68, 228–232.

Huetink, R.E.C., van der Giessen, J.W.B., Noordhuizen, J.P.T.M.,

Ploeger, H.W., 2001. Epidemiology of Cryptosporidium spp.

and Giardia duodenalis on a dairy farm. Vet. Parasitol. 102, 53–

67.

Joachim, A., 2004. Human cryptosporidiosis: an update with special

emphasis on the situation in Europe. J. Vet. Med. B 51, 251–259.

Joachim, A., Krull, T., Schwarzkopf, J., Daugschies, A., 2003.

Prevalence and control of bovine cryptosporidiosis in German

dairy herds. Vet. Parasitol. 112, 227–288.

Lalle, M., Pozio, E., Capelli, G., Bruschi, F., Crotti, D., Caccio,

S.M., 2005. Genetic heterogeneity at the b-giardin locus among

human and animal isolates of Giardia duodenalis and identifica-

tion of potentially zoonotic subgenotypes. Int. J. Parasitol. 35,

207–213.

Lefay, D., Naciri, M., Poirier, P., Chermette, R., 2000. Prevalence of

Cryptosporidium infection in calves in France. Vet. Parasitol. 89,

1–9.

Mohammed, H.O., Wade, S.E., Schaaf, S., 1999. Risk factors

associated with Cryptosporidium parvum infections in dairy

cattle in southeastern New York State. Vet. Parasitol. 83, 1–13.

Monis, P.T., Thompson, R.C.A., 2003. Cryptosporidium and Giar-

dia-zoonoses: fact or fiction? Infect. Genet. Evol. 3, 233–244.

Nygard, K., Vold, L., Robertson, L., Larsen, J., 2003. Underdiag-

nostiseres innenlandssmittede Cryptosporidium-og Giardia-

infeksjoner i Norge? (Article in Norwegian, with english sum-

mary) Tidskr. Nor. Lægeforen. 123, 3406–3409.

O’Handley, R.M., Cocwill, C., McAllister, T.A., Murray, J., Jelinski,

M., Morck, D.W., Olson, M.E., 1999. Duration of naturally

acquired giardiosis and cryptosporidiosis in dairy calves and

their association with diarrhea. J. Am. Vet. Med. Assoc. 214,

391–396.

O’Handley, R.M., Olson, M.E., Fraser, D., Adams, P., Thompson,

R.C.A., 2000. Prevalence and genotypic characterisation of

Giardia in dairy calves from Western Australia and Western

Canada. Vet. Parasitol. 90, 193–200.

O’Handley, R.M., Buret, A.G., McAllister, T.A., Jelinski, M., Olson,

M.E., 2001. Giardiasis in dairy calves: effects of fenbendazole

treatment on intestinal structure and function. Vet. Parasitol. 31,

73–79.

Olson, M.E., McAllister, T.A., Deselliers, L., Morck, D.W., Cheng,

K.-J., Buret, A.G., Ceri, H., 1995. Effects of giardiasis on

production in a domestic ruminant (lamb) model. Am. J. Vet.

Res. 56, 1470–1474.

Olson, M.E., Gusellle, N.J., O’Handley, R.M., Swift, M.L., McAll-

ister, T.A., Jelinski, M.D., Morck, D.W., 1997a. Giardia and

Cryptosporidium in dairy calves in British Columbia. Can. Vet.

J. 38, 703–706.

Olson, M.E., Thorlakson, C.L., Deselliers, L., Morck, D.W., McAll-

ister, T.A., 1997b. Cryptosporidium and Giardia infections in

Canadian farm animals. Vet. Parasitol. 68, 375–381.

Olson, M.E., O’Handley, R.M., Ralston, B.J., McAllister, T.A.,

Thompson, R.C.A., 2004. Update on Cryptosporidium

and Giardia infections in cattle. Trends Parasitol. 20,

185–191.

Ongerth, J.E., Stibbs, H.H., 1989. Prevalence of Cryptosporidium

infections in dairy calves in western Washington. Am. J. Vet.

Res. 50, 1069–1070.

Quılez, J., Sanchez-Acedo, C., del Cacho, E., Clavel, A., Causape,

A.C., 1996. Prevalence of Cryptosporidium and Giardia infec-

tions in cattle in Aragon (northeastern Spain). Vet. Parasitol. 66,

139–146.

Ralston, B.J., McAllister, T.A., Olson, M.E., 2003. Prevalence and

infection pattern of naturally acquired giardiasis and cryptos-

poridiosis in range beef calves and their dams. Vet. Parasitol.

114, 113–122.

Robertson, L., Gjerde, B., 2001. Occurrence of Cryptosporidium

oocyst and Giardia cyst in raw waters in Norway. Scand. J.

Public Health 29, 200–207.

Ruest, N., Faubert, G.M., Couture, Y., 1998. Prevalence and geo-

graphic distribution of Giardia spp. and Cryptosporidium spp. in

dairy farms in Quebec. Can. Vet. J. 39, 697–700.

Santın, M., Trout, J.M., Xiao, L., Zhou, L., Greiner, E., Fayer, R.,

2004. Prevalence and age-related variation of Cryptosporidium

species and genotypes in dairy calves. Vet. Parasitol. 122, 103–

117.

Starkey, S.R., Wade, S.E., Schaaf, S., Mohammed, H.O., 2005.

Incidence of Cryptosporidium parvum in the dairy popula-

tion in a New York city Watershed. Vet. Parasitol. 131, 197–

205.

Sturdee, A.P., Bodley-Tickell, A.T., Archer, A., Chalmers, R.M.,

2003. Long-term study of Cryptosporidium prevalence on a

I.S. Hamnes et al. / Veterinary Parasitology 140 (2006) 204–216216

lowland farm in the United Kingdom. Vet. Parasitol. 116,

97–113.

Thompson, R.C.A., 2004. The zoonotic significance and molecular

epidemiologyofGiardia and giardiasis. Vet. Parasitol. 126,15–35.

Trout, J.M., Santın, M., Greiner, E., Fayer, R., 2004. Prevalence of

Giardia duodenalis genotypes in pre-weaned dairy calves. Vet.

Parasitol. 124, 179–186.

Trout, J.M., Santın, M., Greiner, E., Fayer, R., 2005. Prevalence and

genotypes of Giardia duodenalis in post-weaned dairy calves.

Vet. Parasitol. 130, 177–183.

Uga, S., Matsuo, J., Kono, E., Kimura, K., Inoue, M., Rai, S.K., Ono,

K., 2000. Prevalence of Cryptosporidium parvum infection and

pattern of oocyst shedding in calves in Japan. Vet. Parasitol. 94,

27–32.

Wade, S.E., Mohammed, H.O., Schaaf, S.L., 2000a. Epidemiologic

study of Giardia sp. infection in dairy cattle in southeastern New

York State. Vet. Parasitol. 89, 11–21.

Wade, S.E., Mohammed, H.O., Schaaf, S.L., 2000b. Prevalence of

Giardia sp., Cryptosporidium parvum and Cryptosporidium

muris (C. andersoni) in 109 dairy herds in five counties of

southeastern New York. Vet. Parasitol. 93, 1–11.

Xiao, L., 1994. Giardia infection in farm animals. Parasitol. Today

10, 436–438.

Xiao, L.H., Herd, R.P., 1994. Infection patterns of Cryptosporidium

and Giardia in calves. Vet. Parasitol. 55, 257–262.

Xiao, L., Fayer, R., Ryan, U., Upton, S.J., 2004. Cryptosporidium

taxonomy: recent advances and implications for public health.

Clin. Microbiol. Rev. 17, 72–97.