Preliminary studies on prevalence and importance of goat trypanosomosis in selected farms in Morogoro District, Tanzania

S J Onditi, R S Silayo, S I Kimera*, E N Kimbita and T J N K Mbilu**

Department of Veterinary Microbiology and Parasitology, SokoineUniversityof Agriculture P.O. Box 3019 Morogoro, Tanzania
*Department of Veterinary Medicine and Public Health, Faculty of Veterinary Medicine, Sokoine University of Agriculture, P. O. Box 3015, Morogoro, Tanzania
**current address: National Institute for Medical Research, Tabora Research Center, P. O. box 482 Tabora, Tanzania
togolaimbilu@yahoo.co.uk
 

Abstract

Trypanosomosis is one of the major diseases hindering livestock production in Africa. Many studies have been carried out on the prevalence of the disease in cattle but very little has been done in small ruminants. In Tanzania several reports have been written on livestock diseases in the country, but with very little attention to diseases of small ruminants. The study was undertaken in goats in selected farms in Morogoro, Tanzania, between June and August 2006. The aim was to establish the prevalence rate of trypanosomosis in naturally infected goats and to determine awareness of livestock keepers on the factors contributing to the existence and magnitude of the infection. The methods used included administration of a pre-tested questionnaire to 28 farmers and laboratory diagnosis using thick and thin blood smears as well as buffy coat for the examination of the blood.

A total of 243 goats were sampled, but none of the goats were found to be parasitologically positive for trypanosomosis. The absence of trypanosomes in goats may be due to the control methods used, which included both anti-trypanocidal drugs use and tsetse control. The questionnaire administered to the livestock keepers revealed that most of the livestock keepers in the study area were adults with primary education level with most of them keeping goats and some combining with cattle at the flock size range between 11-20 animals. The major problems hindering livestock production in the study area included water and land scarcity, conflict between livestock keepers and diseases of which the major ones according to them were worm infestation and trypanosomosis. The disease control regime in the area included deworming using Milsan® and Albendazole and prophylaxis using Samorin®at the intervals of three months. A new disease control regime should be /designed in the area to control the disease effectively after having the correct data for production, management, prophylaxis and treatment. This will be obtained through developing proper recording system, laboratory diagnosis, and deployment of traps to establish existence of tsetse in the area.

Keywords: goats, trypanosomosis

Introduction

Livestock production in tropical Africa is greatly hindered by diseases of which tsetse-transmitted trypanosomosis is one of the most important. Ten million square kilometers of Africa are occupied by the tsetse fly transmitting animal trypanosomosis. The disease has caused losses of animals both in terms of meat and milk. It is estimated that over one million tonnes of meat equivalent per year and 1.26 million tonnes of milk per year valued at US dollar 5 billion are being lost (Jahnke et al 1988). It is estimated that approximately 30% of the 147 million cattle in countries affected by tsetse flies are exposed to the risk of infection (FAO/WHO/OIE 1982). In Tanzania two thirds of the land area is occupied by the tsetse fly of which there are seven species namely Glossina morsitans, Glossina pallidipes, Glossina swynnertoni and Glossina austeni occupying the savannah areas, Glossina fuscipes occupying riverine and lake areas, around Lakes Victoria and Tanganyika and Glossina longipennis and G. brevipalpis occupying fringe forests areas. Livestock production is restricted to remaining tsetse free one third of the country as well as on the fringes of the tsetse belts with the help of control measures (Hoare 1972; Stephen 1986). Common trypanosomes found in cattle are Trypanosoma vivax and Trypanosoma congolense. Trypanosoma brucei appears to be uncommon. A study by Connor and Halliwell (1987) on the prevalence of bovine trypanosomosis in southern Tanzania demonstrated that the prevalence was about 16%, of which 56% of the infections were due to Trypanosomacongolense, 17% due to Trypanosoma vivax and 2.2% due to Trypanosoma brucei. Mixed infection comprised 5.4% while 19.4 % were unidentified species.

Small ruminants play an important role in improving the economy of the small farmers, for those who are unable to keep larger animals such as cattle. Goats provide meat, milk, skins, manure and play an important role as liquid assets and source of saving as well as having important religious and social functions such as payment of dowry, celebrations and gifts. Households may liquidate them in times of stress; during drought, agricultural crop failure, and for payment of school fees (Osaer et al 1999). They can survive in a broad ecological zone range including harsh environment, utilize areas which are unsuitable for crop production and feed on a variety of grasses, herbs and shrubs (Oyeyemi 2002). Goat has been reported to be resistant to trypanosomosis (Oladele and Adenegan 1998). However several studies on the prevalence of trypanosomosis in goats in different countries such as Nigeria, Ethiopia and Kenya revealed that goats acquire natural infection resulting in economic losses (Griffin and Allonby 1979; Katunguka 1996; Irungu et al 2002). Infected goats that survive the infection become reservoirs of the parasite for other domestic animals as well as human beings. Goats have been experimentally infected with trypanosomes in studies of experimental trypanosomosis to observe how the infection affects different body parameters such as liveweight, birthweight and reproductive performance like abortion and stillbirth. The experimental infection also affects the haematological changes observed including anaemia, red blood cell count, haemoglobin level and lower packed cell volume in different breeds of goat (Bouteille et al 1988; Mahmoud and El Malik 1977, Azab and Abdel-Maksoud 1999; Tambuwal et al 2002).

In Tanzania there have been several reports on livestock diseases but with very little attention to small ruminants and little on the prevalence of trypanosomosis in goats (Mboera and Kitalyi 1994). This paper presents findings on survey of the occurrence and importance of natural trypanosomosis in goats in selected farms around Morogoro town.
 

Materials and methods

Study area comprised two locations namely Mazimbu Livestock farm located at SUA Mazimbu Campus in Morogoro Municipality and small-holder farms in Gwata Ujembe village, Mikese Ward in Morogoro Rural District. The study areas were selected on the basis of their past history in connection with occurrence of high prevalence of trypanosomosis in goats due to high tsetse challenge. Both areas can be described as bushed grassland with high potential for livestock production.

Animals involved in the study were goats of all ages and both sexes. They were kept under semi-intensive system of management. In Mazimbu farm, goats were grazed extensively on shrubs and pasture around the mountain in absence of cattle. In Gwata village the study goats were kept by individual farmers who grazed them freely along with cattle, but in a few cases they were tethered in absence of cattle.

Both livestock owner's data and experimental data were collected. Data from livestock owners were collected through structured questionnaire while experimental data were collected from blood samples of goat. Blood samples for parasitological examination were collected from a total of 243 goats over a period of two months. Samples were obtained by jugular venipucture into vacutainer tube containing salt of Ethylene- Diamine-Tetra Acetate (EDTA) as an anticoagulant. Each of the tubes were filled up to ¾ of its length and immediately kept cool in ice packs before laboratory examination. In the laboratory the blood samples were screened for trypanosomes using Standard Trypanosome Detection Methods (STDM) namely wet, thick, and thin smear examination as well as the microhaematocrit centrifugation buffy-coat examination as described in (Sewell and Brooklesby 1990). PCV and Buffy coat examination was carried out as described by (Paris et al 1982). Thick and thin smears were prepared from the EDTA preserved blood. Smears were stained with Giemsa at 1:10 dilution for 30 minutes as per standard methods and slides were examined under the microscope at magnification of x100 under oil immersion (Murray et al 1983).

A pre-tested structured livestock keeper's questionnaire was administered to a total of 28 goat keepers used to collect livestock information. The questionnaire assisted to collect information pertaining to goat health, production and husbandry practices in the study area.

For experimental data Stat view program was used for the analysis of Packed Cell Volume (PCV) while SPSS (Statistical Package for Social Sciences) programme was used to analyse livestock owner's information collected through structured questionnaires.
 

Results

In Gwata village, animal health services were delivered by three animal health service providers namely the village extension officer, on-job-trained village animal health attendant and the Bwawani prison farm livestock in-charge. Because there is no recording, it is very difficult to make follow up of the activities done by any individual. Most respondents interviewed were adults aged between 19-45 years dominated by females who account for 53%. The education level for majority of respondents was primary education level (67.9%) with 28.6% having attained secondary school education. The occupations of respondents were farmers (50%), teachers (17.9%) or police/ army officers (25%) and others (7.1%).

Most respondents keep livestock ranging between 11- 20 animals per flock and the majority of them keep goats although some have both goats and cattle. These animals are either tethered around home vicinity (Figure 1) or grazed in bushed grassland (Figure 2). Fifty percent of farmers allow kids to graze at an age of three months, 25% at an age of two months and 21.4% at an age of one month.

Water and land scarcity, conflict between livestock keepers and diseases were the major problems encountered in livestock keeping and the most serious problem was livestock diseases (Figure 3).

Worm infestation was found to be reported by majority of respondents (53%) as a problem encountered in livestock keeping followed by trypanosomosis. Dominex was found to be the frequent used acaricide sprayed once per two weeks (figure 4).

The mean PCV in goats at Mikese area, Morogoro was 20.3% and that obtained from Mazimbu area was 25.5%. PCV was found to be low for those goats which were tethered as compared to those in free range management. Blood samples taken from study area did not reveal any trypanosome parasites in all 243 goats sampled.
 

Discussion

Farmers in the study area keep goats flock of mean size ranging from 11-20. The same range has been reported in Tanzania, Nigeria, Cameroon, and Gambia (Mathewman 1980, Ndamukong 1987; Rawlings et al 1992). The small flock size may be due to problems encountered in livestock production which include water and land scarcity, conflict between livestock keepers and diseases.

Human activities such as bush clearing intended for buildings and cultivation disturb the habitat for tsetse which transmit trypanosomosis (Reid et al 2000 and Thornton et al 2006). In the study area goats were grazed at the bush grassland area which is good habitat for morsitans species of tsetse fly of which two sub-species are found in Tanzania namely Glossina morsitans centalis and Glossina morsitans morsitans (Rodgers and William 1993 and Ministry of Agriculture and Co-operatives 1998).

Trypanosomosis and worm infestation were reported by 25% and 53% of respondents to be the major disease affecting their goats respectively. Results obtained during this study showed that there are no cases of trypanosomosis found in sampled goats. This may be due to several factors including the low feeding success of tsetse on goat related to the small size and anti-feeding behaviour such as leg kicks and stamping, tail and ear flicks, head movement and skin rippling (Vale 1977 and Snow et al 1996). Also biting flies prefer cattle than small ruminants on account of larger size. In communal grazing area they attack cattle and leave most of the small ruminants uninfected (Kniepert 1981). Goats are considered to be resistant to trypanosome infection, showing only a mild or subclinical manifestation of disease under natural condition (Stephen 1970; Oladele and Adenegan 1998). According to the study done by Sinshaw et al (2006) on the prevalence of  trypanosomosis in cattle, small ruminants and equidae, it was revealed that the problem of diagnosis in sheep and goats may be due to existence of some degree of trypanotolerance.

Another reason for the reported low prevalence of trypanosomosis in goats may be due to the weakness of the diagnosis method used, the Standard Trypanosome Detection Methods (STDM). The study done by Connor (1985) on trypanosome prevalence rates in cattle, goats and sheep in Mtwara and Lindi district (Southern Tanzania) using thick and thin blood smears revealed no parasite out of 208 goats sampled. Another study done by Fison (1987) on the prevalence of trypanosomosis in Southern Highlands Region in Tanzania by using the Buffy coat method showed one (1.3%) goat out of 76 goats sampled had the parasites while by using IFAT method out of 514 goats twenty (3.9%) had the parasites. In the study done by Nga'yo et al (2005) on the prevalence of trypanosomosis in small ruminants in Kenya it was demonstrated that by using microscopic method the number of positive samples was five whereas using PCR method number of positive samples increased to 86 out of 402 animals sampled.

Farmers in the study area use Dominex® (cypermethrine), diminazene aceturate and isometamedium chloride for control of tick borne diseases and trypanosomosis. The absence of positive cases in the study area may be contributed to by the use of combination of acaricide and antitrypanosomal drugs (Ilemobade 1988). Deltamethrin has been reported to reduce tsetse fly population by 99% and the trypanosomosis cases in Mkwaja ranch in Tanga region and NARCO ranches in Kagera and nearby farming areas in Bukoba and Karagwe districts (Thompson 1987; Ministry of Agriculture and Co-operatives 1998).

In the study area the average PCV obtained from Mikese and Mazimbu was 20.31% and 25.1% respectively. The minimum and maximum PCV from Mikese area was 15% and 27% respectively whereas in Mazimbu they were 15.5% and 33% respectively. With exception of a few goats most of them have the PCV within the normal range of 22-38% for goats (Dinka and Abebe 2005). The lowest PCV was found in goats which were tethered around the homestead and in those flocks where deworming was not done. The low PCV could be due to high worm infestation and nutrition deficiency. Tethering of goats results in nutritional deficiency, poor body condition, stunted growth and increased contamination of the area with worm eggs infestation due to lack of enough pastures ( Fritsche et al 1993; Kusiluka 1995 and Wassink et al 1997)

The major limitations of the study were the short study period of three months (June to August.). In order to get better results the study would have taken longer period at least 12 months to take care of seasonal changes. In trypanosomosis studies it is better to compare two seasons since the distribution of tsetse flies varies with seasons. Tsetse fly density is higher in rainy seasons than dry season resulting in higher and lower rates of trypanosomosis infection respectively. The method used for the diagnosis had limited sensitivity. It is recommended to use the combination of serological and buffy coat methods for the diagnosis of trypanosomosis to confirm absence or presence of the trypanosomes in the area so that farmers can be advised accordingly.

The combination of using both trypanocidal drugs for prophylaxis and spraying with acaricide for tick control once per week is too expensive for the small holder farmers and it is wastage of resources for the resource-poor farmers. A new disease control regime is needed rather than adopted situation from the past experience since the population of tsetse flies has gone down due to the effect of pyrethroids use for control of ticks in cattle from the adjacent village (Bwawani prison farm). Further studies on prevalence of trypanosomosis should be done using more sophisticated techniques such as PCR in order to confirm the absence of this disease. Also this can help to test the sensitivity of STDM and PCR. Recording system for the farmers must be developed to obtain the correct data for production, management, prophylaxis and treatment. The animal health services in the village should be provided by a trained village extension officer. If provided by others then it must be recorded properly to obtain the correct data. In order to establish the disease condition and give correct advise to farmers all suspected cases should be confirmed by laboratory diagnosis and more survey studies done on prevalence of the disease including the deployment of traps to establish presence or absence of tsetse population and species present in the area.

Acknowledgement

We would like to thank the Government of Tanzania through the Ministry of Livestock Development for sponsoring the study to enable S.J.O. to obtain the Master of Preventive Veterinary Medicine (MPVM) degree. We would also like to thank Mr. A S Kitime of Department of Veterinary Medicine and Public health and Mr. K A Lekaki of Department of Veterinary Microbiology and Parasitology for technical assistance and advice to S J O. We would like to gratefully acknowledge the assistance and cooperation received from the District Agriculture and Livestock Development Office (DALDO's office) Morogoro and the extension officers in the study area. The livestock keepers at Mikese Ward and Mazimbu Farm are thanked for allowing us to interview them and sample their animals.

Lastly, all those who in one way or another, assisted in the completion of the work from which this paper emanates are gratefully acknowledged. May God bless them all.
 

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Received 3 March 2007; Accepted 23 March 2007; Published 1 May 2007

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