TRYPANOSOMOSIS AND OTHER PARASITIC DISEASES AFFECTING SHEEP AND GOATS PRODUCTION IN TWO GROUP RANCHES, NAROK DISTRICT, KENYA.

LA TRYPANOSOMOSE ET LES AUTRES MALADIES PARASITAIRES AFFECTANT LA PRODUCTION BOVINE ET CAPRINE DANS DEUX RANCHES COMMUNAUTAIRES DANS LE DISTRICT DE NAROK AU KENYA

J.O.Wesongah1, J.Chemulitti1, F.D. Wesonga2, L.Munga1, P.Ngare1 & G.A. Murilla1

1 Kenya Trypanosomiasis Research Institute, P.O. Box 362, Kikuyu, Kenya
2 KARI/NVRC P.O.Box 32, Kikuyu, Kenya

Résumé

            Une étude transversale a été menée dans des ranches communautaires de Lemek et de Koyaki, dans le district de Narok, pour enquêter sur les principales maladies qui affectent la production de petits ruminants. Les méthodes parasitologique et de flottation saline de MacMaster ont été utilisées pour recueillir des données sur la prévalence de la maladie. Les résultats ont révélé que les principales maladies qui affectent les petits ruminants étaient l’helminthiase, la cowdriose et la trypanosomose. Les nématodes les plus répandus dans la zone étaient les strongyloïdes et les strongyles qui, en général, attaquent simultanément la plupart des animaux. Pendant la saison des pluies, le taux global de prévalence de la trypanosomose chez les moutons et les chèvres était de 1,3 % (2) et de 4,6 % (7) respectivement, et ce taux baissait considérablement (p<0,05) jusqu’à atteindre 0 % (0 caprin) et montait jusqu’à 2 % (3 ovins) pendant la saison sèche. Les taux globaux de prévalence de l’helminthiase pendant la saison des pluies chez les moutons et les chèvres étaient de 60 % (54) et 72 % (78) respectivement avant le déparasitage au Nilzan Plus (1,5 % de Levamisole plus l’hydrochlorure de refoxanide). Après le déparasitage des animaux, le taux de prévalence est descendu à 32,5 % (27) et à 43,5 % (37) respectivement chez les moutons et chez les chèvres pendant la saison sèche. La prévalence globale de la cowdriose était beaucoup plus élevée (p<0,05) chez les moutons (69 %, 101) que chez les chèvres (47 %, 70), de même que le nombre de tiques. En conclusion, l’on peut dire que les principales maladies qui affectent les petits ruminants sont l’helminthiase, la cowdriose et la trypanosomose. Cette étude a recommandé aux éleveurs des stratégies appropriées de lutte contre ces trois maladies, lors d’un atelier et à travers des recherches supplémentaires pendant une période de surveillance plus longue (2 ans) sur les maladies animales qui affectent la production de petits ruminants.

Summary

            A cross-sectional study was carried out in Lemek and Koyaki group ranches, Narok district to investigate important diseases affecting small ruminants production.   Parasitological and MacMaster salt floatation methods were used to collect data on disease prevalence.  The findings showed that the most important diseases affecting small ruminants were helminthosis, heartwater and trypanosomosis.  The most prevalent nematodes identified were strongyloides and strongyles, which usually occurred together in most animals.  The overall prevalence rates for helminthosis during the wet season in sheep and goats were 60%(54) and 72% (78) respectively before deworming with Nilzan plus (1.5% levamisole plus refoxanide hydrochloride).  After deworming the animals, the prevalence declined to 32.5% (27) and 43.5% (37) in sheep and goats respectively during the dry season.  During the wet season the overall trypanosomosis prevalence in sheep and goats was 1.3%(2) and 4.6 % (7) respectively and decreased significantly (p<0.05) to 0% (0 goats) and increased to 2 % (3 sheep) during the dry season. The overall prevalence of heartwater was significantly higher (p<0.05) in sheep (69 %, 101) than in goats (47%, 70) as well as the tick numbers.  During the study 3/300 animals died due to helminthosis but this was not significant (p>0.05).  In conclusion the most important diseases affecting small ruminants are helminthosis, heartwater and trypanosomosis.  This study recommended appropriate control strategies for the three diseases to farmers through a feedback workshop and further research with longer monitoring period (2 years) on animal diseases affecting small ruminant production.

Introduction

            Sheep and goats are mainly found in arid and semi-arid areas of sub-Saharan Africa.  They play a vital role in rural economies through the provision of meat, milk, household income, manure, and skin.  Compared to cattle and camels, sheep and goats contribute a larger proportion of readily available meat in the diets of pastoralists12.  They have been estimated to provide up to 30% of the meat and 15% of the milk supplies in sub-Saharan Africa 5 where they thrive in a wide range of ecological regions often in conditions too harsh for the beneficial rearing of cattle.  Small ruminants have also been reported to survive better under drought conditions than cattle due to their low body mass and low metabolic requirements, which minimizes their water requirements and maintenance needs in arid and semi-arid areas 15.  The frequent droughts and large tsetse infested areas in sub-Saharan Africa calls for a need to keep more small ruminants in order to supplement cattle production.

            Chemotherapy is the most common method used for controlling parasitic diseases such as trypanosomosis and gastro-intestinal helminthosis, which are a major hindrance to the development of agriculture and the livestock industry.  However, frequent use of veterinary drugs in livestock production has been reported to lead to the development of drug resistance under natural conditions 9,14.  Small ruminants unlike cattle have been reported to be less susceptible to trypanosomosis so they are treated less frequently or do not require trypanocidal treatment 12,17.  Studies carried out on epidemiology of trypanosomosis in sheep and goats in Kenya under ranch and Maasai pastoral management systems indicate differences in susceptibility between sheep and goats and between local and exotic breeds under different production systems 7,12,4.  A cross sectional study carried out to quantify the production and constraints of sheep and goats under traditional Maasai pastoral management in Kajiado district by Mwendia 12, indicated that the main disease control measures undertaken by the pastoralists were chemotherapy and avoiding areas associated with high disease transmission.  Field studies were carried out by Griffin Allonby 3 on the economic effects of trypanosomosis in sheep and goats using three different trypanocidal drugs (Isometamidium chloride, Quinapyramine and Diminazene aceturate) at a range land research station in Makueni district, Kenya.  These authors reported that prophylactic treatment, perhaps coupled with other more permanent methods such as bush clearing of controlling the disease, would have an important beneficial effect on the productivity of sheep and goats in the range areas, even when tsetse challenge is low.

            Narok district, a semi arid area of Kenya, is endemic for trypanosomosis and other livestock diseases such as helminthosis (Narok district development plan, 2000).  The main economic activity is livestock production and tourism.  Livestock population in Narok district is estimated at 1,250,258 thousand heads of which, 45% are sheep, 10% are goats and the rest are cattle.  It is anticipated that improving their productivity by controlling livestock diseases will inevitably alleviate the prevailing poverty through increased household incomes.  There is no objective information on disease prevalence and control measures undertaken in this area.  The present study was carried out in an attempt to address the identified gaps in knowledge on small ruminant production in Narok district, Kenya.

Materials and Methods

Study Site

            The study was carried out in three randomly selected villages (Emorijoi, Ngoswani and Enkoje) situated in two group ranches Lemek and Koyaki in Narok district, Kenya.  The two group ranches lies approximately between latitude 1o 00’ and 2 o 00’ south and longitude 34o 45’ and 36o 00 East.  The area covers about 6,000km2.  and borders Tanzania in the south, Siria escarpment to the west, Loita plains and hills to the east and Siana hills to the south-east.  The area and can be divided into 3 Eco-units based on the biography and climate 16 which includes Mara Reserve, Siana (south-east of the reserve) and Loita (north reserve).  During the study period (March to December 2003) the temperature recorded ranged from 13 oC to 33 oC while the annual rainfall was approximately 554 mm.

Selection of farmers

            Ten farmers were conveniently selected from two villages Emorjoi and Ngoswani in Lemek group ranch because they participated in a previous study involving cattle.  Five farmers were purposively selected from Enkoje village in Koyaki group ranch due to the high tsetse challenge recorded in the area.  Ten sheep and an equal number of goats were randomly selected from each of the fifteen farmers.  Each farmer had approximately 120 small ruminants.  The total number of experimental animals selected was 300 (150 sheep and 150 goats). 

Experimental animals

            The experimental animals selected were indigenous.  The goats consisted of galla and small East Africa while the sheep consisted of black head somali and Red Maasai.  The small ruminants selected consisted of 143 females (135 adults and 8 lambs) and 157 males (146 adults, 1 lamb and 10 kids).  All the experimental animals were eartagged for identification.  The experimental animals were grazed on extensive grassland without boundaries.  The small ruminants were grazed near the Bomas while the cattle were grazed far away from the Bomas.  All the experimental animals were clinically examined and weighed using a weighing balance.  Animals that were sick or with wounds were treated appropriately immediately after examination. 

            All the experimental animals were dewormed with Nilzan plus (1.5 % levamisole plus Refoxanide hydrochloride-Levafas, Norbrook Laboratories Ltd) at a dose per drug of 7.5 mg/kg body weight during the wet season.  Animals found to be positive for trypanosomes were treated with diminazene aceturate at 7mg/kg body weight.

Sampling technique/study visits

            For each visit, animals in the same herds were bled.  Blood samples for sera were collected aseptically by jugular venipuncture into plain vacutainer tubes (Becton-Dickinson) from all the experimental animals.  Blood was also collected into heparinised capillary tubes for parasitaemia and PCV determination.

Study visits to all the three study sites were undertaken on a seasonal basis (once during the rains and once during the dry season plus a farmer selection visit, April to October 2003) giving three visits per homestead.

Diagnosis of trypanosomes

            Buffy coat concentration method was used to detect trypanosome infections while haematocrit centrifugation technique was used for PCV determination 11. Giemsa stained thin blood smears were used for identification of different trypanosome species.

Haemoparasites:

            Thick and thin blood smears were prepared on glass slides for observation for haemoparasites.

Serum preparation and IB ELISA

            The blood was left to clot at room temperature for 4 hours followed by storage overnight at +4 oC.  The following day it was centrifuged at 1200 g for 30 minutes, serum was separated and stored in aliquots of 2 ml at -20 oC.  The sera was then analyzed for antibody against Cowdria ruminantium that is transmitted by ticks of the genus Amblyomma using the indirect map (major antigenic protein) 1B ELISA 8.

Tsetse challenge

            The tsetse challenge was monitored monthly using biconical traps set once a month in the areas where animals grazed 1

Tick sampling

            All the experimental animals were sampled for ticks by counting and identifying the type of ticks on the whole body using the body (B), tail (T), leg (L) and head (H) tick count method 13

Feacal egg count (FEC)

            Feacal samples were collected from all the experimental animals early in the morning.  The animals were sampled at the same time of the day and a large sample size was used to reduce the variation usually observed in faecal egg counts (FEC).  The method used in this study was MacMaster salt floatation technique2.

Results

Tsetse challenge

            The tsetse species identified in the 3 villages were mainly Glossina swynnertoni and G. pallidipes.

The tsetse challenge was recorded from March to September, 2003 as Fly per trap per day (FTD) and this ranged from (0-31.1) with the highest being 31.1 recorded in August in Enkoje village.

Prevalence of trypanosomosis

Goats

            The overall trypanosomosis prevalence recorded in goats during the wet season was 4.6% (7) and decreased to 0% (0) during the dry season in the three villages.

In Enkoje village during the wet season the point trypanosomosis prevalence recorded was 14 % (7) in goats and reduced to 0% (0) during the dry season.

However in the Emorojoi and Ngoswani villages no trypanosome infections were detected in goats throughout the study period.

Sheep

            The overall trypanosome prevalence in sheep was 1.3% (2) during the wet season and increased to 2%(1) during the dry season but this was not significant (P>0.05). 

In Enkoje village the point trypanosomosis prevalence recorded in sheep during the wet season was 10 % (5) and decreased to 6 % (3) during the dry season.  Similar to goats no trypanosome infections were detected in sheep in Emorojoi and Ngoswani villages.

            The trypanosome species identified in Enkoje village were T. congolense (58.3%,7) and T. vivax (41.7% ,5 ) in the two animal species during the two seasons (Table 1).  Trypanosomosis had no significant (P>0.05) effect on the PCV recorded in both species.

Table1: Trypanosome infections in sheep and goats from three different villages in Narok district

            The overall helminthosis prevalence recorded in goats was 72% (78).  The (epg) ≥1000 recorded in goats in the three villages sampled were Emorijoi (19%,11) Ngoswani (6%, 2) and Enkoje (4.4%, 4 ) before deworming with (Nilzan plus).  The egg per gram (epg) ≥1000 declined to 2 % in Enkoje village and to zero in the other 2 villages after deworming.  The coccidia prevalence recorded was 33.5%.

Sheep

            The overall helminthosis prevalence recorded in goats was 60% (54).  The (epg) ≥1000 in the three villages sampled was (22%,12) in Emorijoi, (12.5%, 5) in Ngoswani and

(3 %,3) in Enkoje before deworming and declined to less than 7 % in the 3 villages sampled after deworming.  The coccidia prevalence recorded was 30 %.

The most prevalent nematode species identified in the two animal species were strongyles and strongyloides.  The worm load had a significant (P<0.05) negative effect on the PCV of both sheep and goats.

Tick counts

Goats

            During the wet season the total tick counts in Emorijoi, Ngoswani and Enkoje villages recorded in goats ranged from 0-625, 0-71 and 0-120 respectively (Table 2).

Sheep

            During the wet season the total tick counts in Emorijoi, Ngoswani and Enkoje recorded in sheep ranged from 0-854, 0-309 and 0-600 in the three villages respectively (Table 2).

The most common tick species was Rhipicephallus appendiculatus in the two animal species.  Other tick species observed were B. decoloratus, R. Evertis, H. marginatum and A. variegatum. 

Table 2: Tick counts and heartwater prevalence in sheep and goats recorded in three different villages in Narok district

nd=not done

Tick borne diseases

            No heamoparasites were observed during the survey in the two species. Prevalence of heartwater

Goats

            The prevalence of antibodies to E. ruminantium in goats was significantly higher P<0.05 in Emorijoi than the other two villages Ngoswani and Enkoje villages as shown in Table 2.  This was consistent with the higher counts of the vector tick Amblyomma variegatum in Emorojoi

Sheep

            The prevalence of antibodies to E. ruminantium in goats was significantly higher P<0.05 in Ngoswani (82.5% 33) than Emorijoi and Enkoje as shown in Table 2. However this was not consistent with the total tick  recorded in the area. The  Amblyomma  species identified during the dry season in both species were higher (>5) compared to the wet season.

Discussion

            In this study indigenous sheep and goats were found to be with trypanosomosis as well as helminths.  A similar observation was made by Mwendia 12 .  Heartwater was also found prevalent in the study site where livestock under pastoral production system.  The overall trypanosomosis prevalence recorded in goats was 4.6% and 1.3% in sheep and decreased significantly (p<0.05) to 0% in goats and increased to 2% in sheep but this was not significant (p>0.05).  The observed decrease in trypanosomosis prevalence in goats could be attributed to the low tsetse challenge (range, 0-31.1FTD) recorded during the study.  Two trypanosome species, Trypanosoma congolense (47%, 5) and Trypanosoma vivax (58%, 7) were identified in the two animal species with the latter being more common in goats than sheep.  This is the first report of trypanosome infections in small ruminants in the study area.  Previous studies in Narok district have mainly focused on cattle where trypanosomosis prevalence rate was reported as 5-6% 10.

            The findings of this study do indicate that even in areas where tsetse challenge is low trypanosome infections can be detected in small ruminants thus they may act as reservoirs for cattle if left untreated.  Previous studies on trypanosomosis and productivity constraints in small ruminants had similar findings 6,12.  However, trypanosome infections had no significant effect on PCV in sheep and goats, as occurs in cattle.  Further studies are needed to establish why this is the case.  The differences observed in trypanosome infections between the three villages may be attributed to differences in the tsetse challenge or management practises.  The low trypanosomosis incidence observed in the study area may be managed by proper diagnosis followed by treatment of individual animals with diminazene aceturate. The effect on weight could not be drawn because the animals were monitored for only three months.

            The gastrointestinal helminths observed in both species were mainly strongyle or strongyloides.  Animals with high worm burdens were found to have low PCVs, which is a measure of anaemia indicating a negative effect on the health of the animals.  However the helminth infections decreased significantly during the dry season.  This may be attributed to a combination of factors such as the intervention applied or the change in season as the helminth eggs do not survive well on pastures during the dry season.  Coccidia was also observed in a number of young animals and this could be the cause of diarrhaoea cases reported by farmers.

            This survey also revealed that heartwater is prevalent in small ruminants in Emorijoi, Ngoswani and Enkoje villages of Narok district.  The prevalence of heartwater was significantly higher (P<0.05) in sheep (69 %, 101) than in goats (47%, 70) in the three villages sampled and same applied to the tick numbers.  This could be attributed to differences in the grazing habits of the two animal species where goats are mainly browsers while sheep are grazers and the wool in sheep to which ticks can easily attach compared to goats.  Previous studies carried out on small ruminant production constraints 12 based heartwater diagnosis on clinical signs and referred to his findings as unconfirmed.  However in this study an antibody ELISA which is highly specific test for Ehrlichia cowdria was used to test for cowdria infection thus rendering the findings as a confirmation of the disease in the study area.

            In conclusion this study recommends management of trypanosomosis in small ruminants by proper diagnosis and use of diminazene aceturate.  For effective management of helminthosis and heartwater strategic deworming and spraying of the animals respectively is recommended.  Finally a longitudinal study is recommeded to establish the effect of trypanosomes, cowdria and helminth on small ruminant productivity

Acknowledgments

            We wish to thank the Government of Kenya for funding this study, the Center director KARI-TRC and the management for facilitation.  Dr. R.E Mdachi and Mr. G.N. Ngae for the statistical analysis.  The authors highly appreciated the technical assistance given by the epidemiology and residue analysis technical staff, and for data analysis, KARI/NVRC, Muguga staff for sample analysis and their good co-operation and all the farmers who allowed us to their animals.  This paper is published with the kind permission of the Director, KARI.

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