Venomous snakes in Morocco: biogeography and envenomation Serpents venimeux du Maroc: biogéographie...

Publié le: 2013-05-22

Venomous snakes in Morocco: biogeography and envenomation

Serpents venimeux du Maroc: biogéographie et envenimation

Auteurs :Hamida Argaz, Soumia Fahd, José Carlos Brito

Catégorie : Environnement > Biologie

ScienceLib Editions Mersenne : Volume 5 , N ° 130509ISSN 2111-4706

www.sciencelib.fr

Venomous snakes in Morocco: biogeography and envenomation

Serpents venimeux du Maroc: biogéographie et envenimation

Hamida Argaz1,*, Soumia Fahd1, José Carlos Brito2

1 Laboratoire “Diversité et Conservation des Systèmes Biologiques”. Faculté des Sciences de

Tétouan, Université Abdelmalek Essaâdi. Tétouan, Maroc

2 CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do

Porto, Vairão, Portugal

*Corresponding author: E-mail address: [email protected]

Abstract

Morocco with its 112 amphibians and reptiles is one of the richest countries in the

Mediterranean Basin. Venomous snakes are represented by two families: Elapidae (1 species)

and Viperidae (7 species). Envenomation by snakebite represents a health problem in

Morocco. As a first step to address this phenomenon, we updated distribution maps for each

species: Daboia mauritanica was found to be the most abundant and widely distributed

venomous snake while Echis leucogaster was the rarest and more restricted one. Secondly, we

developed a preliminary epidemiological survey in the Community of Tangier-Tetouan

(Northern Morocco). In the region, the rate of snakebite victims is 8.6/100,000 inhabitants

during 2004 to 2008, the species causing more envenomation was D. mauritanica, the age of

victims ranged between 12 and 60 year old, and both sexes were equally affected. Snakebite

occurred mostly between April and September, roughly coinciding with the activity season of

D. mauritanica.

KEYWORDS: Elapidae; Morocco; Snakebite; Venom, Viper; Viperidae

Résumé

Le Maroc est l'un des pays les plus riches de la Méditerranée en termes d’herpétofaune. Ce

sont en effet pas moins de 112 espèces d’amphibiens et de reptiles qui constituent son

herpétofaune. Les serpents venimeux sont représentés quant à eux par deux familles: Elapidae

Hamida Argaz

ScienceLib Editions Mersenne : Volume 5 , N ° 130509 ISSN 2111-4706

mailto:[email protected]

(1 espèce) et Viperidae (7 espèces). Une carte de distribution actualisée a été élaborée pour

chacune de ces espèces, Daboia mauritanica est la plus abondante et la plus largement

répartie, Echis leucogaster étant ponctuelle et rarissime. D’autre part, l'envenimation par

morsures de serpents venimeux représente un grave problème de santé au Maroc. Dans un

premier temps, ce phénomène a été étudié dans la Province de Tanger-Tétouan. Cette étude

préliminaire a montré que le taux d'envenimation est de 8,6/100 000 habitant durant 2004-

2008. L’espèce qui cause le plus d’envenimations par morsure est D. mauritanica. L’âge des

patients varie entre 12 et 60 ans, les deux sexes étant affectés. La période d’atteinte par

morsure correspond généralement à la période s’étalant entre les mois de mai à septembre.

Elle coïncide avec la période d’activité des vipères dans cette région du pays.

MOTS-CLES: Elapidae, Maroc; Morsures de Serpents; Venin; Viperidae.

Hamida Argaz


1. INTRODUCTION

In the Mediterranean basin, Morocco is one of the richest places in terms of animal and plant

diversity. It possesses the richest and most varied herpetofauna in the Maghreb and the

western Mediterranean, and is characterized by high species richness, endemism and number

of European relict species [1]. This originality is caused by the importance of its mountains,

grouped into four chains (Rif, Middle, and High and Anti atlas). The Moroccan herpetofauna

is represented by 112 species of amphibians and reptiles [2].

Snakes are represented by 27 species among which eight are venomous. Venomous snakes are

represented by two families: Elapidae represented by one specie only, and Viperidae that has

7 distinct species. Snakebite envenoming constitutes a highly relevant public health issue on a

global basis, although it has been systematically neglected by health authorities in many parts

of the world [3, 4]. Annually, there are about 5 million cases of snakebites, causing 150,000

deaths, mainly in the tropical countries [5]. In Africa, there are 500,000 estimated cases of

envenomation each year resulting in more than 20,000 fatalities, and a high morbidity

frequently resulting in agonizing suffering and often severe sequel, such as necrosis of limbs

leading to amputation or disability [6]. According to the Moroccan poison control center, 217

cases of ophidian envenomation were declared during 2001 to 2003, a mortality rate of about

4%, and most accidents occurring in southern rural areas [7].

This work has two objectives: 1) to update distribution maps of venomous snakes in Morocco;

2) to make an epidemiological study of snakebite cases in the province of Tetouan.

2. MATERIALS AND METHODS

2. 1. Study area

The region of Tetouan (35° 34'21" North, 5° 21'17" West) is located in the extreme north-

western Morocco, and is limited by the Gibraltar Strait and Mediterranean Sea in the north, by

the Atlantic Ocean in the west, by the region of Gharb in the south, and by the region of Taza-

Al hoceima Taounat in the east (Fig. 1).

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Fig 1: Location of the study area Tangier-Tetouan region

2.2. Distribution of Moroccan venomous snakes

To update the distribution of species, we first elaborated a georeferenced database of species

observations. Observations were collected over a period of more than two decades by two

research groups based in Morocco (LDICOSYB, Faculty of Sciences in Tetuan) and Portugal

(CIBIO, Universidade do Porto). Bibliographical observations were also compiled in the

database. Species distribution maps were using a Geographical Information System, ArcGIS

9.3 (ESRI, USA).

2. 3. Envenomation

Inquiries were conducted in health centres and hospitals of the Study area Tetouan during

2004 to 2008. The health institutions visited were the Tetouan Civil Hospital, M'diq Hospital,

and Oued Laou health centres. The information on envenomed patients treated was examined

to identify cases of snakebite. Interviews were conducted to doctors and nurses for additional

valuable information on the subject. Data were considered for analyses only in cases where

complete information on sex, age, and health evolution of the patient, and period and locality

of accident were available.

3. RESULTS

3. 1. Distribution of venomous snakes in Morocco

Updated distribution maps for the venomous snakes presented in Morocco allow identifying

the following distributions patterns: 1) Vipera latastei (Bosca 1878): the Lataste’s viper is

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known from 15 localities (Fig 2) scattered by the Rif and Middle Atlas mountains and it

occurs in various Mediterranean habitats subjected to relatively high rainfall, from coastal

dunes to 2000 m in Djbel Bouhalla; 2) Vipera monticola (Saint Girons 1954): the Atlas dwarf

viper is a Moroccan endemic known from 31 localities (Fig 3) in the High and the Middle

Atlases, and it is found in screes, stones and cushion-like thorny plants, at altitudes ranging

between 1200 to 2178 m in the Middle Atlas, and from 2400 to 3900 m in the High Atlas; 3)

Daboia mauritanica (Gray 1849): the Maghrebian viper is known from 134 localities (Fig 4)

encompassing the whole of Mediterranean Morocco, and it is abundant in the arid and semi-

arid zones; 4) Cerastes cerastes (L.1758): the Horned viper in known from 92 localities (Fig.

5) distributed by the Sahara fringes and southern Morocco; 5) Cerastes vipera (L.1758): the

sand Viper is known from 42 localities (Fig.6) covering aeolian or coastal sand formations

subjected to Saharan climate; 6) Bitis arietans (Merrem 1820): the Puff adder is known from

39 localities (Fig.7) with a localized distribution in southern coastal areas; 7) Echis

leucogaster (Roman1972): the White-bellied carpet viper is the rarest snake in Morocco,

known only from seven localities (Fig.8). 8) Naja haje (L. 1758): the Egyptian cobra is the

only representative of the family Elapidae and it is known from 51 localities (Fig.9) occurring

mainly in the arid and Saharan bioclimatic zones with warm or temperate winters.

Fig 2: Distribution map of Vipera latastei in Morocco

Fig 3: Distribution map of Vipera monticola in Morocco

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Fig 4: Distribution map of Daboia mauritanica in Morocco

Fig 5: Distribution map of Cerastes cerastes in Morocco

Fig 6: Distribution map of Cerastes vipera in Morocco

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Fig 7: Distribution map of Bitis arietans in Morocco

Fig 8: Distribution map of Echis leucogaster in Morocco

Fig 9: Distribution map of Naja haje in Morocco

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3. 2. Envenomation by snakebite

A total of 45 snakebite cases were treated in Tetouan region during 2004 to 2008 (Fig 10). All

patients received at Tetouan hospital got a treatment. Bites were more frequent during the hot

season, between April and September (Fig 11). The age of victims varies between 12 and 60

years. Patients were from both sexes, but males were more bitten than females. A high

proportion of bites occurred on the lower limbs, while others were located on the feet and

hands.

Fig 10: Records of venomous snakebite in the region of Tetouan (N=45)

Fig 11: Monthly variation in the occurrence of venomous snakebite in the region of

Tetouan (n = 17)

Hamida Argaz


3.3 Snakebite treatment

According to the inquiries made to doctors and nurses, patients administered at the hospitals

received urgently similar treatments including the Venox, paracetamol, antibiotics, and

hydrocortisol. The first treatments of ophidian envenomation focused on symptoms, in which

the patients are administrated with drugs against pain, fever and against potential infection.

After that, a monitoring treatment is carried out for 4 hours to follow possible instabilities in

vital organs, such as heart, liver, and nervous system. Such instabilities are characterized by

an early vomiting, hypertension, shock cardiac, renal dysfunction and respiratory

complications. In such cases, the patient is moved to the intensive reanimation bloc,

connected to multiple machines under critical surveillance. If the vital organs are not reached,

the aforementioned treatment is sufficient to heal the patient. The mean duration of

hospitalization the patients was 3, 7 days (Fig. 12).

0

2

4

6

1 2 3 4 5 6 7 8 9 10 11 12

1

65

12

10

10 0 0

1

Frequency

Number of days

Fig 12: Distribution of patients (n = 18) depending on the duration of hospitalization

4. DISCUSSION

Of the eight species of venomous snakes existing in Morocco, D mauritanica is the most

abundant specie and widely distributed. E leucogaster is expanded to the north of Morocco,

and is the rarest and punctual snake across the country.

Rate of victims in the province of Tetouan was about 8.6/100,000 inhabitants. This number

was insignificant compared to the entire population, it must be highlighted that the number of

snakebite victims is probably underestimated. Indeed, victims consult in priority traditional

practitioners who always do not advice them to go to modern health centers medical

institutions. In the opposite, snake bites represent a serious health problem in the central

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region of Morocco, particularly Souss-Massa-Daraa with 447 cases (31.4%), and Marrakech-

Tensift-Al Haouz with 353 cases (24.8%) [8], the higher incidence in these two regions could

be explained by their large population, but also by the diverse fauna of snakes living there [9,

10].

Identification of the viper species could not be achieved because victims were unable to

identify the snakes. Usually, after biting occurs, snakes flee or hide quickly and victims were

unaware of the names and are unable to identify them. Probably, mainly accidents were due to

the bite of snakes from the D. mauritanica, the most abundant and common viper in Tetouan

Province.

The Accidents of snakebite were frequent during the hot period between April and September,

which probably related to the activity period of snakes [11]. This observation is similar to the

results obtained in other studies [8, 12, 13], but for other authors, snake bites were reported

more frequently between November and April [14, 15].

In addition, most bites happened during the daytime, unlike the night prevalence reported in

other studies [12, 16, 17]. This may be due by the fact that human activity is essentially

diurnal [14]. With the regard to the accident place, the majority of the cases occurred in the

rural zone [15].

Predominant age group was composed of young adults and adolescents, mainly due to their

greater exposure through outdoor activities, particularly agricultural ones [14, 18, 19, 15, 20].

Which reflects that a high incidence of attack on males than females. Similar results were

reported by numerous studies in many countries, respectively in turkey, Saudi Arabia,

Bangladesh and India: [21, 12, 22, 23].

CONCLUSION

According to the results obtained, we can conclude that snake bites do not represent a real

danger to in our study area population. In addition to this, the number of snakebite victims is

probably underestimated, because many victims do not attend to medical institutions.

Hamida Argaz


Conflict of Interest Statement

The authors have declared that no conflict of interest exists

Acknowledgements

This study was partially supported by cooperation CNRST (Maroc) and FCT (GRICES.

Portugal) (Project 889-08/09). The authors would like to thank the Department of Public

Health of Morocco for authorizing access to archives of medical facilities.

Hamida Argaz


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