This art icle was downloaded by: [ Abiodun Adewale]On: 06 July 2011, At : 20: 25Publisher: Taylor & FrancisI nforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mort imerHouse, 37-41 Mort imer St reet , London W1T 3JH, UK

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Frequency of Detection of Immunoglobulins ofToxoplasma gondii, Leptospira spp. , and Brucellaabortus in Livestock/ Farm and Abattoir Workers inTrinidadAbiodun Adesiyun DVMMPHPhD a , Mervyn Campbel l DVMMS a , Saed Rahaman DVMMPH b

, Sham Bissessar DVMMPVM b , Alva St ewart -Johnson BScMSc a , Shakt i Dookeran BSc a &

Marquit a Git t ens-St . Hilaire PhD c

a School of Vet erinary Medicine, Facult y of Medical Sciences, Universit y of t he WestIndies, St . August ine, Trinidad and Tobagob Vet erinary Publ ic Healt h Unit , Minist ry of Healt h, Port of Spain, Trinidad and Tobagoc Lept ospira Laborat ory, Minist ry of Healt h, St . Michael, Barbados

Available onl ine: 05 Jul 2011

To cite this article: Abiodun Adesiyun DVMMPHPhD, Mervyn Campbel l DVMMS, Saed Rahaman DVMMPH, Sham BissessarDVMMPVM, Alva St ewart -Johnson BScMSc, Shakt i Dookeran BSc & Marquit a Git t ens-St . Hilaire PhD (2011): Frequency ofDet ect ion of Immunoglobul ins of Toxoplasma gondi i , Lept ospira spp. , and Brucel la abor t us in Livest ock/ Farm and Abat t oirWorkers in Trinidad, Journal of Agromedicine, 16:3, 200-209

To link to this article: ht t p: / / dx.doi.org/ 10.1080/ 1059924X.2011.581541

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Journal of Agromedicine, 16:200–209, 2011

Copyright © Taylor & Francis Group, LLC

ISSN: 1059-924X print/1545-0813 online

DOI: 10.1080/1059924X.2011.581541

Frequency of Detection of Immunoglobulins of Toxoplasma

gondii, Leptospira spp., and Brucella abortus in

Livestock/Farm and Abattoir Workers in Trinidad

Abiodun Adesiyun, DVM, MPH, PhD

Mervyn Campbell, DVM, MS

Saed Rahaman, DVM, MPH

Sham Bissessar, DVM, MPVM

Alva Stewart-Johnson, BSc, MSc

Shakti Dookeran, BSc

Marquita Gittens-St. Hilaire, PhD

ABSTRACT. Toxoplasma gondi, Leptospira spp., and Brucella abortus are all established parasitic

and bacterial zoonoses that manifest themselves in several forms of human diseases. They have been

associated with occupational exposures, particularly amongst workers associated with livestock farms.

The primary objectives of this study were to determine the seroprevalence of T. gondii immunoglob-

ulin M (IgM) immunoglobulins (serum antibodies), Leptospira IgM immunoglobulins, and B. abortus

IgG immunoglobulins, suggestive of acute or chronic infections, in livestock/farm and abattoir work-

ers in Trinidad, and to relate to risk factors. Blood samples were collected from 394 consenting

livestock/farm workers and 99 abattoir workers across the island of Trinidad. Serological status was

determined by enzyme immunoassay (EIA) for T. gondii IgM, enzyme-linked immunosorbent assay

(ELISA) for Leptospira IgM immunoglobulins, and buffered plate agglutination test (BPAT) and com-

petitive ELISA for B. abortus IgG immunoglobulins. Of 394 apparently healthy livestock/farm workers

sampled, 150 (38.1%) were seropositive for T. gondii IgM immunoglobulins, compared with 44 (44.4%)

of 99 abattoir workers (p > .05; χ2 test). Five (1.3%) of 371 and 1 (1.0%) of 99 livestock/farm and

abattoir workers respectively were positive for Leptospira IgM immunoglobulins. All samples from

livestock/farm workers and abattoir workers were negative for B. abortus immunoglobulins. None of

the risk factors investigated was statistically significantly (p > .05; χ2 test) associated with T. gondii

and Leptospira spp. infections.

Abiodun Adesiyun, Mervyn Campbell, Alva Stewart-Johnson, and Shakti Dookeran are affiliated with theSchool of Veterinary Medicine, Faculty of Medical Sciences, University of the West Indies, St. Augustine,Trinidad and Tobago.

Saed Rahaman and Sham Bissessar are affiliated with the Veterinary Public Health Unit, Ministry ofHealth, Port of Spain, Trinidad and Tobago.

Marquita Gittens-St. Hilaire is affiliated with the Leptospira Laboratory, Ministry of Health, St. Michael,Barbados.

The authors appreciate the contributions of the technical staff of the Veterinary Public Health Unit of theMinistry of Health for assisting in the completion of questionnaires during the study. The authors acknowl-edge the input of Gerard Ramirez for drawing blood from all participants in the study. The authors thank thegovernment of Trinidad and Tobago for funding the project.

Address correspondence to: Abiodun Adesiyun, School of Veterinary Medicine, Faculty of MedicalSciences, University of the West Indies, St. Augustine, Trinidad and Tobago (E-mail: Abiodun.Adesiyun@sta.uwi.edu).

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KEYWORDS. Abattoir workers, brucellosis, farm and livestock workers, leptospirosis, Trinidad and

Tobago, toxoplasmosis

INTRODUCTION

Toxoplasmosis is a parasitic zoonosis

recognized worldwide with reported variable

rates in apparently healthy individuals in

the population.1,2 The parasite, Toxoplasma

gondii, may be transmitted to humans by

various routes, including consumption of rare

or undercooked meat containing the cyst form

of the pathogen, ingestion of oocysts shed in cat

feces, and eating poorly washed raw fruits or

vegetables.3–5 The occurrence of toxoplasmosis

has been associated with several occupational

exposures.6,7 For general population studies,

detection of T. gondii immunoglobulin G (IgG)

immunoglobulins is used as evidence of past

infections.8,9 Acute infections, as demonstrated

by detection of T. gondii IgM, or clinical

manifestation has been shown to cause abor-

tion, miscarriages, and blindness in children

whose mothers acquired primary infection

during pregnancy10,11 and blindness or other

manifestations in adulthood.12

The use of IgM detection as evidence of

acute/current infection by T. gondii has its

limitation because IgM immunoglobulins may

remain for extended periods.13 The sensitivity

and specificity of commercial test kits avail-

able to detect T. gondii infections also affect

reported incidence and prevalence of toxoplas-

mosis in both animals and humans.14 In Trinidad

and Tobago, serological evidence of toxoplas-

mosis has been reported for dogs,15 slaugh-

ter livestock,16 goats on a breeding farm,17

and pregnant women at antenatal clinics,18 and

recently Adesiyun et al.19 provided the first evi-

dence of congenital toxoplasmosis in humans

using cord blood samples. There has also been

a documentation of T. gondii IgM immunoglob-

ulins in sugar cane workers in the country.20

Leptospirosis is associated with a spectrum

of clinical manifestations in humans,21,22 but

a majority of infections have been reported to

be asymptomatic.23 Infections by Leptospira

serovars have been linked to certain occu-

pations such as farm workers, veterinarians,

and abattoir workers,24,25 with seroprevalence

higher than those reported for the general

human population.26 In Trinidad and Tobago,

the last published report on human leptospiro-

sis was in 1989 when clinical leptospirosis

was reported in piggery workers,27 whereas

Leptospira seroprevalence rates ranging from

5% to 37% have been documented in appar-

ently healthy individuals.28–30 Most recently,

Adesiyun et al.31 reported the seroprevalence of

Leptospira infection in different types of dog

populations.

Brucellosis is a disease of socioeconomic

and public health importance internationally.32

In humans, it causes a wide variety of clini-

cal manifestations.33,34 In countries where the

disease is endemic in animals, human brucel-

losis has been reported, particularly in occupa-

tionally exposed individuals.35 In Trinidad and

Tobago, the Office of International Epizooties

(OIE) brucellosis-free status was lost in 1998

with the demonstration of brucellosis by culture

and serology in cattle and water buffalo.36,37

There is a dearth of information on the occur-

rence of acute or current T. gondii, Leptospira

spp., and Brucella abortus infections in the

population of individuals at risk. The study

was therefore conducted to determine the fre-

quency of detection of IgM immunoglobulins

to T. gondii and Leptospira spp. and IgG

immunoglobulins to B. abortus in individuals

who worked on livestock farms and abattoirs

in Trinidad and to relate demographic data and

practices to infection.

MATERIALS AND METHODS

Sources of Samples

Through the participation of the Veterinary

Public Health Unit (VPHU) of the Ministry

of Health, personnel at all large private live-

stock and institutional farms and at abattoirs or

slaughter slabs associated with these farms were

contacted to solicit their voluntary participation

in the study. The study design was to collect

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202 ZOONOSES IN FARM AND ABATTOIR WORKERS

TABLE 1. Sources of Human Samples From Livestock Farms and

Abattoir Studied

Identification of sources of samples

(type of animals)

Livestock/farm

workers∗

Abattoir/slaughter

house workers∗

Number of

workers

Number (%)

of workers

tested

Number of

workers

Number (%)

of workers

Erin Farm (pig) 54 24 (44.4) 14 13 (92.9)

Miller Farm (mixed)† 26 17 (65.4) 1 1 (100.0)

Sugar cane feed center (mixed) 69 41 (59.4) 8 8 (100.0)

University field station (mixed) 42 31 (73.8) 3 3 (100.0)

Centeno Farm Centre (mixed) 86 31 (36.0) 1 1 (100.0)

Smithsfield Farm (pig) 34 28 (82.4) 8 8 (100.0)

ECIAF‡ (mixed) 62 20 (32.3) NA NA

Quarantine station‡ 48 38 (79.2) NA NA

Artificial insemination center (cattle) 49 32 (65.3) NA NA

Aripo Livestock Farm (mixed) 147 83 (56.5) NA NA

Waller Field§ 5 5 (100.0) NA NA

South Animal Health Office§ 65 26 (40.0) NA NA

Mora Valley (water buffalo) 12 12 (100.0) NA NA

Ministry of Agriculture Rio Claro§ 10 6 (60.0) NA NA

Chaguanas abattoir NA NA 32 17 (53.1)

Port of Spain abattoir NA NA 33 26 (78.8)

Arima abattoir NA NA 8 2 (25.0)

San Fernando abattoir NA NA 69 20 (29.0)

Total 709 394 (55.6) 177 99 (55.9)

∗Number of workers who volunteered to participate in the study and were available for sampling.†Rearing sheep, goats, cattle, pigs, and/or fish.‡East Crribbean Institute of Agriculture and Forestry.§Offices where animal health assistants, veterinarians, and office assistants take calls for cases from

farms.

NA = not applicable.

blood samples from consenting individuals.

Sampling schedules were discussed with the

managers of the various farms. Overall, sam-

ples were collected from individuals/farmers at

10 farms/institutional farms across the country

(Table 1). Of the 394 farm workers, the common

activities performed were as follows: laborers

(86 workers), laboratory technicians/equipment

operators/storekeepers (70), stockmen (31),

veterinarians/poultry and dairy farmers (40),

animal health assistants (37), supervisors (22),

and others (108). Among the 99 abattoir workers

from 10 abattoirs/slaughter facilities, duties per-

formed were as follows: slaughtering/dressing

of carcasses/handling of offal (39), dressing of

carcasses only (7), slaughtering only (6), han-

dling of offal only (5), and other duties, which

occurred at lower frequencies. Sampling was

done between April and June 2006.

Approval by Ethics Committee

The Ethics Committee of the Ministry of

Health approved the research protocol before the

study commenced.

Sampling Protocol

The Veterinary Public Health Unit of

the Ministry of Health, which coordinated

access to farms and abattoir studied, ini-

tially contacted all institutional farms owned

by agencies associated with the govern-

ment and a total of 10 farms comprising

three large farms (over 2000 animals) in the

country were studied. The study was also

performed at the 10 abattoirs/slaughterhouses

in the country functional at the time of the

study. Table 1 shows the identity of the

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Adesiyun et al. 203

farms and abattoirs and the number of

personnel who volunteered and participated in

the study.

All workers were informed of the volun-

tary nature of the project and during the vis-

its each participant completed a consent form.

In addition, each consenting participant com-

pleted a questionnaire that elicited demographic

data (ethnic group, age, marital status, gender,

and number of children) and other risk factors

for toxoplasmosis, leptospirosis, and brucellosis

(types of duties performed by different cate-

gories of workers).

Collection of Blood Samples

To collect blood samples, qualified phle-

botomists drew 5 ml of blood from the median

veins of each individual into Vacutainer tubes

without anticoagulant. Blood samples were

transported to the laboratory ice-cooled and

stored overnight at 4◦C, after which serum was

harvested following centrifugation. Serum sam-

ples were thereafter stored at −20◦C until tested.

Detection of Immunoglobulins in Serum

Samples

The Toxoplasma IgM Capture enzyme

immunoassay (EIA) test kit (Diamedix, Miami,

USA), with appropriate positive and negative

controls supplied by the manufacturer, was used

to detect to IgM immunoglobulins to T. gondii.

The current study is part of a larger cross-

sectional investigation to detect immunoglob-

ulins to pathogens (bacterial, parasitic, viral)

in apparently healthy livestock farm, sugarcane

field, and abattoir/slaughterhouse workers in

Trinidad. The strategy to assay for T. gondi IgM

immunoglobulins in this cross-sectional study

was therefore to make a presumptive qualitative

detection using index values of 1.10 or greater

to interpret as positive. Since the design of the

study did not allow for repeat testing, all equiv-

ocal test results with index values of 0.90 to

1.09 were therefore considered to be negative

together with samples with index values less

than 0.90. Finally, since the objective was sim-

ply to presumptively screen for T. gondii IgM

immunoglobulins in an apparently healthy pop-

ulation, this study did not assay for or compare

with T. gondii IgG results. The limitations in

interpreting the results of the assay as stipulated

by the manufacturer were indicated in the dis-

cussion of the results of the study, particularly

highlighting the possibility of false-positive and

false-negative test results. Other than the above

stated modifications in interpreting the results,

the EIAs were performed using the methodology

stipulated by the kit manufacturer. This included

transferring frozen serum samples to refriger-

ators at 4◦C overnight and in the morning of

testing, sera were allowed to attain room temper-

ature (25◦C) and mixed gently before testing.

To detect Leptospira IgM immunoglobu-

lins, an enzyme-linked immunosorbent assay

(ELISA) as described was used38 with serovar

Patoc as antigen and an IgM titer of 160 or

higher was regarded as positive. The buffered

plate agglutination test (BPAT) was used to test

for B. abortus agglutinins39 followed by the

competitive ELISA40 for BPAT-suspect posi-

tive samples.

Analysis of Data

The seroprevalence of T. gondii IgM

immunoglobulins, Leptospira IgM immunoglo-

bulins, and B. abortus IgG immunoglobulins by

category of workers as well as any possible rela-

tionship between risk factors and seroprevalence

for T. gondii infection were analyzed using the

Statistical Package for Social Sciences (SPSS),

version 10. All statistical tests were two-sided

and interpreted at the 5% level of significance

using the chi-square (χ2) test.

RESULTS

The seroprevalence of T. gondii IgM

agglutinins was 38.1% (150 of 394) for

livestock/farm workers compared with 44.4%

(44 of 99) for abattoir workers, but the differ-

ence was not statistically significant (p > .05;

χ2 test), as shown in Table 2. Leptospira

spp. IgM immunoglobulins were detected in

5 (1.3%) of 371 livestock/farm workers but in

only 1 (1.0%) of 99 abattoir workers. All sam-

ples tested from livestock/farm workers (394)

and abattoir workers (99) were seronegative for

B. abortus immunoglobulins.

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204 ZOONOSES IN FARM AND ABATTOIR WORKERS

TABLE 2. Seroprevalence of Toxoplasmosis, Leptospirosis, and

Brucellosis in Livestock/Farm and Abattoir Workers

Type of infection Category of workers

Livestock/farm workers Abattoir workers

Number tested Number (%)

seropositive

Number tested Number (%)

seropositive

Toxoplasmosis∗ 394 150 (38.1) 99 44 (44.4)

Leptospirosis† 371 5 (1.2) 99 1 (1.0)

Brucellosis‡ 394 0 (0.0) 99 0 (0.0)

∗Using enzyme immunoassay (EIA) for T. gondii IgM.†Using the enzyme-linked immunosorbent assay (ELISA) for IgM immunoglobulins

with titers of 1:160 and higher regarded as positive.‡Using the buffered plate agglutination test (BPAT) and cELISA.

TABLE 3. Seroprevalence of Toxoplasma gondii

IgM Immunoglobulins in Livestock/Farm

Workers

Characteristic

of worker

Number of

workers

tested

Number (%) of workers

seropositive∗ for T. gondii

immunoglobulins

Gender

Male 313 119 (38.0)

Female 81 31 (38.3)

Race

African 241 86 (35.7)

Indian 124 51 (41.1)

Others† 29 13 (44.8)

Age (years)

<20 9 5 (55.6)

21–30 70 35 (50.0)

31–40 101 41 (40.6)

41–50 98 32 (32.7)

>50 113 36 (31.9)

NA 3 1 (33.3)

Type of job

High risk‡ 235 98 (41.7)

Others§ 159 52 (32.7)

∗Using enzyme immunoassay (EIA).†Chinese, Syrians, mixed races.‡Farm laborers/attendants/handy men, stockmen, animal

health assistants, poultry and dairy farm workers.§Delivery personnel, supervisors, security officers, drivers,

laboratory technicians.

NA = not available.

None of the risk factors (demographic charac-

teristics and practices) investigated had a statis-

tically significantly (p > .05; χ2 test) association

with T. gondii infection in livestock or farm

workers (Table 3).

TABLE 4. Seroprevalence of Toxoplasma gondii

IgM Immunoglobulins in Abattoir Workers

Characteristic of

worker

Number of

workers

tested

Number (%) of workers

seropositive∗ for T. gondii

immunoglobulins

Gender

Male 92 39 (42.4)

Female 7 5 (71.4)

Race

African 51 25 (49.0)

Indian 44 18 (40.9)

Others† 4 1 (25.0)

Age (years)

<20 1 1 (100.0)

21–30 18 10 (55.6)

31–40 16 6 (37.5)

41–50 26 11 (42.3)

>50 38 16 (42.1)

Type of job

Slaughtering 32 13 (40.6)

Dressing and

handling offals

18 8 (44.4)

Others‡ 49 23 (46.9)

∗Using enzyme immunoassay (EIA).†Chinese, Syrians, mixed races.‡Supervisors, office workers.

Amongst abattoir workers, the seroprevalence

of T. gondii IgM immunoglobulins was similar

for various demographic and risk factors stud-

ied (p > .05; χ2 test), as displayed in Table 4.

The seroprevalence was, however, higher in

female than in male workers and in people of

African origin compared with individuals of

Indians origin.

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TABLE 5. Seroprevalence of Leptospira IgM

Immunoglobulins in Livestock Farm Workers

Category of

workers

Number of

workers

tested

Number (%) of workers

seropositive∗ for

Leptospira spp.

immunoglobulins

Gender

Male 293 5 (1.7)

Female 78 0 (0.0)

Race

Indian 224 3 (1.3)

African 122 2 (1.6)

Others∗∗ 25 0 (0.0)

Age (years)

<20 8 0 (0.0)

21–30 67 1 (1.5)

31–40 93 2 (2.2)

41–50 90 1 (1.1)

>50 110 1 (0.9)

Unknown 3 0 (0.0)

Type of job

High risk∗∗∗ 222 2 (0.9)

Others∗∗∗∗ 149 3 (2.0)

∗Using enzyme immunoassay (EIA).∗∗Chinese, Syrians, mixed races.∗∗∗Farm laborers/attendants/handy men, stockmen, animal

health assistants, poultry and dairy farm workers.∗∗∗∗Delivery personnel, supervisors, security officers,

drivers, laboratory technicians.

All five farm workers seropositive for

Leptospira IgM immunoglobulins were male

workers with a seroprevalence of 1.7%

(Table 5). Race, age, and type of job performed

by workers did not significantly affect the fre-

quency of infection by Leptospira spp. (p > .05;

χ2 test).

The lone Leptospira-seropositive abattoir

worker was an East Indian male, aged 31 to

40 years, whose responsibility was slaughter-

ing animals.

DISCUSSION

The seroprevalence of 38.1% for T. gondii IgM

immunoglobulins detected in livestock/farm

workers in the country is very high compared

with levels reported in studies where T. gondii

IgM immunoglobulins were also assayed for in

sugarcane workers in the country20 using the

same methodology, where 15.7% (64 of 407)

were also positive for T. gondii IgM. This is

perhaps not surprising given that farm workers

are a high-risk group for toxoplasmosis, as are

slaughterhouse workers, veterinarians, and meat

inspectors, amongst other individuals.6,41,42 The

high seroprevalence detected in the current study

may also reflect the testing strategy used where

the seropositive individuals were considered

presumptive because it did not concurrently

assay and compare with T. gondii IgG. There

is therefore a possibility of false-positive test

results simply based on the test strategy and

interpretation used. Considerably lower rates of

seroprevalence (IgM) for toxoplasmosis have

been reported for apparently healthy people

in Turkey, 2.33%1; Thailand, 4.3%43; India,

4.4%44; and Bahrain, 10.3%.45 It should, how-

ever, be emphasized that there is a need to

exercise caution in comparing seroprevalence

rates with other populations due to differences

in test methodologies and interpretations, partic-

ularly using commercial test kits with varying

validity.

It has been reported that a positive test result

for T. gondii IgM immunoglobulins may indi-

cate an acute infection, a reactivated infection,

or it could be an older infection with resid-

ual IgM immunoglobulins, which may linger in

the circulatory system for months. False-positive

and sometimes false-negative results have there-

fore been associated with screening for T. gondii

IgM immunoglobulins using commercial test

kits.3,13,14,46

In an earlier study in Trinidad and Tobago

on pregnant women sampled at health cen-

ters and antenatal clinics, a seroprevalence of

7.6% was reported.18 Of public health signif-

icance is the high seroprevalence of T. gondii

IgM immunoglobulins in adult farm workers,

which included women of child-bearing age,

since it has been demonstrated that acute infec-

tion may lead to abortion or miscarriage in

pregnant women, blindness, and other health

problems.10–12 Although the pregnancy status of

the seropositive women, 41.4% (36 of 87), in

the current study was not determined, the risk

cannot be ignored.

It is equally important that of all the demo-

graphic factors (age, sex, and race) and type of

jobs (contact or lack of direct animals contact)

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206 ZOONOSES IN FARM AND ABATTOIR WORKERS

studied, none was statistically significantly asso-

ciated with infection by T. gondii amongst the

workers. It is, however, pertinent to mention

that the groups of workers studied were simi-

lar regarding exposure to toxoplasmosis, which

may be different from community controls.

Similar findings were reported for earlier stud-

ies in the country18–20 and elsewhere.44,47 In

other studies amongst high-risk groups, toxo-

plasmosis has been reported to be significantly

associated with similar risk factors (demogra-

phy or types of jobs performed) by animal farm

workers.41,48

The seroprevalence of 44.1% for T. gondii

IgM immunoglobulins detected amongst slaugh-

terhouse or abattoir workers in the current study

is considerably higher than the rates reported

for slaughterhouse workers in China, 2.32%48;

Saudi Arabia, 20.0%49; and India, 2%.50 It is of

interest to note that the high rate of T. gondii

IgM immunoglobulins found in this study is

higher than the seroprevalence rates deter-

mined with T. gondii IgG immunoglobulins, also

using the enzyme-linked immunosorbent assay

(ELISA), in Japan, 32.8%41; Finland, 25%42;

and Egypt, 19.2%.51 It has been documented

that in apparently healthy populations the

seroprevalence rates for toxoplasmosis assayed

by IgG (existing/chronic infection) always far

exceeded those that test for IgM (acute/current

infection).19,52 This is because it is expected

that the evidence of past or chronic infec-

tions will be higher in apparently healthy peo-

ple in the general population. Again, as found

in farm workers, this difference in findings

may be explained by a possibility of false-

positive results with the assay system and strat-

egy used in the current study. As found for

livestock/farm workers, all the risk factors stud-

ied did not significantly affect seroprevalence

of T. gondii IgM immunoglobulins, contrary to

published reports by others on slaughterhouse

workers where similar risk factors were demon-

strated to be significantly linked to T. gondii

infection.41,44,48,53

The finding in the current study that for both

farm and abattoir workers, the type of work done

by the workers, for example handling of animals

on farms versus drivers or slaughtering/dressing

carcasses versus office workers/supervisors

in abattoirs/slaughterhouses, did not signifi-

cantly affect the prevalence of T. gondii IgM

immunoglobulins is an interesting one. Possible

explanations include that the supervisor/office

worker group has unreported occupational expo-

sures that are similar to the other risk groups, or

that both groups have been exposed outside the

workplace (e.g., contaminated water or food in

the community).

The seroprevalence of leptospirosis as

detected by Leptospira IgM is low in both

known high-risk groups for the disease,

livestock/farm workers (1.4%) and abattoir

workers (1.0%), in the current study. This

suggests that acute/current leptospirosis is

uncommon in studied high-risk groups in

the country. The low prevalence is compa-

rable to the rates reported in Chile, 3.3%54;

Puerto Rico, 6%–24%55; and Vietnam, 5.4%56;

but significantly lower compared with sero-

prevalence reported for apparently healthy

people in Trinidad and Tobago, which ranged

from 5% to 37%,28–30 using the microscopic

agglutination test (MAT), which detects IgG

immunoglobulins.57 It is well known that

subclinical infections by Leptospira spp. are far

more prevalent than acute/current infections,

which constitute the tip of the iceberg.58 This

does not suggest the lack of documentation of

clinical leptospirosis in the country, since the

disease has been reported in piggery workers

and hospitalized patients.26,59,60 In other coun-

tries, investigators using the MAT to screen for

leptospirosis amongst farm and abattoir workers

have reported prevalence rates ranging from

13.1% to 67%.6,23,25,61

The small number of seropositive

livestock/farm workers and abattoir work-

ers identified in the current study makes it

difficult to assess the relationship of risk factors

of these groups of workers to infection by

Leptospira spp. Risk factors such as type of

job, gender, age, and prevalence of leptospirosis

in animals handled, amongst others, have been

associated with leptospirosis.23,24,62

It was hardly a surprise that all serum sam-

ples tested for B. abortus IgG immunoglobulins

were negative for brucellosis. This is because

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Trinidad and Tobago was certified by the OIE

as brucellosis-free until 1998 when that status

was lost with confirmed (serological and iso-

lation) cases of brucellosis in cattle and water

buffaloes.36,37 Realizing the economic and pub-

lic health significance of the disease, the govern-

ment of Trinidad and Tobago has successfully

implemented a test and slaughter policy using

the BPAT and c-ELISA for serosurveillance.

The policy and measures taken to prevent the

spread of brucellosis in livestock population in

the country through strict restriction of move-

ment of infected herds effectively controlled the

disease and therefore prevented human expo-

sure. In other countries where brucellosis is

endemic in the livestock populations, the dis-

ease has been reported in slaughterhouse and

farm workers,6,63–65 emphasizing its zoonotic

significance.

It is concluded that of the three zoonoses

(toxoplasmosis, leptospirosis, and brucellosis)

tested, current/acute toxoplasmosis was most

prevalent amongst farm and abattoir workers

studied, whereas infections by Leptospira spp.

and B. abortus were very low and nonexistent,

respectively.

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