Livestock farmers' perception and epidemiology of bovine trypanosomosis in Kwale District, Kenya

We did cross-sectional surveys in Kwale District, Kenya to determine the epidemiology of bovine trypanosomosis and livestock owners' perceptions of the disease. The surveys involved relative importance of trypanosomosis, examination of the current disease constraints, current control practices and drug-use patterns. Informal meetings were held with farmers and cattle census undertaken. Tsetse-fly densities and trypanosomosis prevalences in cattle were determined. A total of 132 farmers were interviewed. Trypanosomosis, anaplasmosis, East Coast fever, foot-and-mouth diseases were reported to be the major constraints to livestock production. Trypanosomosis was the most important compared to other diseases. Chemotherapy was the most widely used method of controlling the disease. Farmer-based tsetse-control technologies were poorly adopted. Respondents were quite knowledgeable on the symptoms, causes and treatment of trypanosomosis. Glossina austeni, G. brevipalpis and G. pallidipes were found in the area; the latter was the most common (0.2-738 flies/trap). Trypanosoma congolense and T. vivax were found in cattle with the former more prevalent. Infection prevalences in cattle varied between 0 and 25% (median: 22%).     

Implications of the re-invasion of Southeast Uganda by Glossina pallidipes on the epidemiology of bovine trypanosomosis

A study to assess the influence of re-invasion of Glossina pallidipes on the epidemiology of bovine trypanosomosis was conducted in Southeast Uganda. A total of 1,992 cattle were screened in villages, with (949) and without G. pallidipes (1043) for trypanosomosis using a combination of the BCT and HCT methods. The prevalence of trypanosomosis (15.5%), Trypanosoma brucei infection (1.4%), T. congolense infection (7.2%), T. vivax infection (5.3%) and mixed infection (1.6%) in cattle in villages with was significantly higher than in those without G. pallidipes: trypanosomosis (7.1%), T. brucei infection (0.6%), T. congolense infection (2.0%), T. vivax infection (3.3%) and mixed infection (1.2%) (overall trypanosome infection, chi2=35.5, d.f.=1, P<0.05; T. brucei infection, chi2=8.06, d.f.=1, P<0.05; T. congolense infection, chi2=22.8, d.f.=1, P<0.05 and T. vivax infection, chi2=6.4, d.f.=1, P<0.05). Infections of Trypanosoma congolense were predominant in cattle in villages with G. pallidipes, while T. vivax infections were predominant in cattle in villages without. In all villages, T. brucei infections were fewer than either T. congolense or T. vivax infections. The risk of transmission of T. brucei, T. congolense and T. vivax infections was 3, 2.7 and 1.6 times, respectively, higher in villages with G. pallidipes than in those without, despite the presence of G. f. fuscipes in either set of villages. The mean PCV (28.27+/-0.41, 95% CI) and mean herd size (3+/-0.46) of cattle in villages with G. pallidipes were significantly (P<0.05) lower than in those in villages without (mean PCV, 29.48+/-0.34; mean herd size, 4+/-0.72). It is evident that presence of G. pallidipes brings about an increase in the prevalence of T. congolense, which causes a more severe disease in cattle than other species of trypanosomes. This is a rare case of a re-invasion of a tsetse species whose disease transmission capability calls for refocusing of the traditional national tsetse and trypanosomosis control strategies to contain it.     

Modelling bovine trypanosomosis spatial distribution by GIS in an agro-pastoral zone of Burkina Faso

Modelling of the spatial distribution of bovine trypanosomosis prevalence in Sideradougou district Burkina Faso was performed by using a combination of spatial and statistical analysis. Based on a comprehensive and geographically representative census of herds and farms in the area, more than 2000 cattle were randomly chosen and their blood sampled during field survey. Data on livestock farming practices were recorded for each farm. All data were mapped within a GIS to generate new information on spatial constraints in the area.Surveys results were analysed and serological prevalence data were modelled using logistic regression. The model allowed identification and quantification of risk factors. In a second step the statistical model was used predictively on the entire farm population in the area. This method was successful in predicting the serological prevalence for each individual herd in the sample, from their livestock management patterns and spatial location. Predicted prevalences were represented within the GIS, taking daily movements of animals into account. Spatial distribution of prevalence would illustrate specific locations at risk from an epidemiological viewpoint. It gives evidence that the hydrological network and land occupation patterns in the savanna-type countryside are playing an important part when structuring a so-called "trypanosomosis space".     

The area-wide epidemiology of bovine trypanosomosis and its impact on mixed farming in subhumid West Africa; a case study in Togo.

This paper reports on an area wide study of all major variables determining the expression of trypanosomosis in cattle in the subhumid eco-zone of West Africa, taking Togo as an example. To enable systematic area-wide sampling, the country was divided in 311 grid-squares of 0.125 x 0.125 sides. Cross-sectional surveys were then conducted to generate maps or digital layers on cattle density, herd structure, ownership and breed. These data layers, except for the breed data, were subjected to a cluster analysis in order to define spatial patterns in animal husbandry systems. This analysis revealed two main systems: one is oriented towards integration with crop-agriculture and a second towards investment in cattle. These two systems could be further characterised by incorporating breed data. Zebu cattle and their crossbreeds are more favoured in the second system. The breed distribution map shows the actual situation but also serves to predict the outcome of progressive crossbreeding. An area wide trypanosomosis survey allowed the production of prevalence maps for Trypanosoma congolense, T. vivax and the associated packed cell volume (PCV) values. A simple curvi-linear relationship was established between vector density and disease prevalence. The regression between disease prevalence and PCV for taurine and zebu plus crossbreeds separately, revealed that taurine cattle maintain a comparatively high PCV level particularly in high prevalence scenarios. The relationship between the average herd PCV and cattle density suggests that herd PCV value may provide a mirror for the number of animals not kept because of the prevailing risk. The regression between agricultural intensity and cattle density subsequently in areas with decreasing herd PCV values reveals that the level of integration of cattle in crop production decreases with a decreasing PCV. Thus, despite the presence of taurine animals in Togo, the omnipresence of tsetse in particular Glossina tachinoides, remains a major obstacle to cattle raising and indirectly mixed farming development and intensification. It is argued that only with the present type of wide scale, spatial studies it becomes possible to clarify all the major variables influencing the expression of trypanosomosis. Spatial epidemiological studies at a macro level may form the basis for area wide trypanosomosis control in West Africa.     

The distribution of tsetse (Diptera: Glossinidae) and bovine trypanosomosis in the Matutuine District, Maputo Province, Mozambique

A tsetse and bovine trypanosomosis survey was conducted during 1998 and 1999 in the Matutuine District of Maputo Province (Mozambique). A total of 59 Glossina brevipalpis and 17 Glossina austeni were captured throughout the district. Survey results suggest that Glossina brevipalpis is mainly concentrated in dense vegetation along the Maputo River and in the wetlands east of the river. G. austeni, on the other hand, was captured mainly in dense thickets in drier areas. Both tsetse species are suspected to be vectors of bovine trypanosomosis. Bovine trypanosomosis (75,5% Trypanosoma congolense) was diagnosed in 53 animals (13,9%) from seven sampling sites distributed throughout the district. The prevalence of cattle with anti-trypanosomal antibodies was high (29,9%).The incidence of trypanosomal infections in sentinel cattle was also high. The widespread distribution of bovine trypanosomosis and the high prevalence of infection are likely to have a significant impact on cattle production and, hence, the cattle restocking exercise in the district.     

The epidemiology of bovine dermatophilosis in Zambia

Bovine dermatophilosis (Senkobo disease) has been reported annually in Zambia for many years. However, its epidemiology under Zambian conditions had never been adequately studied. Officially the disease has never been recognized as being of any economic consequence.A field study was designed and conducted from August to December 1986, to provide estimates of epidemiological statistics and other factors for the period January 1985 to December 1986 in four districts. These districts supported approximately 28% of the national cattle herd. The study was conducted in communally grazed herds as the disease was reportedly of little significance in commercial herds. A total of 365 herds containing 22 344 head of cattle were inspected and the owners interviewed; 286 herds (78.4%) and 1114 cattle (5.0%) were found to be affected. Rainy weather, vegetation type such as grass savannah, woodland savannah and thorny bush, ticks and biting flies were indicated as important factors in the appearance and course of dermatophilosis in Zambia.     

The epidemiology of bovine trypanosomiasis in Colombia

Summary A review is given of the present knowledge of the epidemiology of bovine trypanosomiasis in Colombia. Search of the literature, discussions with veterinarians, and original observations have given information on the distribution and prevalence of the pathogenicTrypanosoma vivax and non-pathogenicT. theileri-like organisms.T. evansi infections of cattle may exist but were not detected. Improved methods of diagnosis forT. vivax are required to elucidate problems of: differentiating clinically similar diseases; the susceptibility of cattle relative to age; transmission; wild animal reservoirs, and economic importance. The indirect fluorescent antibody test is an important technique to this end.

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Sumario Se hace una revisión del conocimiento actual de la epidemiología de la tripa nosomiasis bovina en la república de Colombia. La revisión de literatura, de talladas discusiones con médicos Veterinariosy observaciones personales han proporcionado información sobre la distribución y prevalencia delT. vivax (uno de los tripanosomas patógenos) y de los tripanosomas semejantes alT. theileri (un tripanosoma no patógeno). ElT. evansi es posible que exista en los vacunos pero no fué detectado. Se requieren mejores métodos de diagnóstico paraT. vivax con el objeto de aclarar problemas tales como: diferenciación clínica de enfermedades simila res; la susceptibilidad de los bovinos según su edad; métodos de transmisión; el papel de los animales salvajes como reservorios y la importacia económica de las tripanosomiasis. Para conseguir estos objectivos se requiere el uso de la técnica de la fluorescencia indirecta de anticuerpos.

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Résumé Il s’agit d’une revue des connaissances actuelles sur l’épidémiologie de la trypanosomose bovine en Colombie. Des recherches bibliographiques, des entretiens avec les vétérinaires et des observations originales ont permis d’acquérir des renseignements sur la distribution et l’importance deT. vivax pathogène et d’un trypanosome non pathogène ressemblant àT. theileri. Les infections du bétail àT. evansi peuvent exister, mais n’ont pas été décelées. Des méthodes améliorées de diagnostic sont nécessaires pourT. vivax afin d’élucider certains problèmes: diagnostic différentiel avec des maladies cliniquement semblables, sensibilité du bétail en fonction de son age, transmission, animaux sauvages ‘réservoirs’, importance économique. On suggère que la méthode d’immunofluorescence indirecte pourrait être très utile à ces fins.

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E. A. Wells 10th April, 1967–12th July, 1967, and 4th Sept., 1969–13th Dec., 1969; W. A. Page, 7th Sept., 1969–13th Dec., 1969.     

Antibody-ELISA seroprevalence of bovine trypanosomosis in the Eastern Province of Zambia

A longitudinal study was conducted over a 1-year period in six selected villages in Petauke and Katete districts in the Eastern Province of Zambia. Starting in November 1997, 50 animals were sampled at random at each village every 2 months. The parasitological prevalence of trypanosomosis was determined by the haematocrit centrifugation buffy-coat technique, supplemented with thick and thin Giemsa-stained blood films. Serum samples also were collected for anti-trypanosomal antibody determination by indirect enzyme-linked immunosorbent assay.

Parasitological prevalence was highly variable between villages and between visits (range: 0–28.6%; median: 3.1%). Seroprevalence was also variable between villages (range: 0–80.8%; median: 50%), but was less variable between visits. Average annual parasitological prevalence and average annual seroprevalence for each village were highly correlated [R² (adjusted for d.f.)=0.89, p<0.01]. Seroprevalence measured on any single visit to a study village was better than parasitological prevalence as a predictor of average annual parasitological prevalence.     

Prevalence of bovine trypanosomosis in Central Mozambique from 2002 to 2005

The study is the result of analyzing 16895 blood smears of cattle collected at 180 sites in the provinces of Manica, Sofala, Zambézia and Tete in Mozambique. Of the blood smears 73.9% were from Manica, 11.8% from Tete, 8.5% from Sofala and 5.8% from Zambézia; 75.6% of these were collected from smallholder cattle. Infections with trypanosomes were highest in smallholder cattle from Sofala Province with 36.8% of the 872 blood smears examined positive for trypanosomes, and lowest in cattle of commercial farmers in Manica Province with only 6.2% of 2252 blood smears being positive. Trypanosoma congolense was the predominant species, followed by Trypanosoma vivax and Trypanosoma brucei sensu lato. Trypanosoma brucei, which also infects humans, was more frequent in the districts of Buzi, Mutarara and Morrumbala with 15.1%, 10.5% and 9.8% of all examined cattle in 2005 being infected with it, respectively. The results show a significant increase in the infection rate with trypanosomes compared with results obtained in previous years by the Regional Veterinary Laboratory in Manica Province and by the Regional Tsetse and Trypanosomiasis Control Programme in Zambézia, Tete and Sofala provinces.     

The medicine and epidemiology of bovine respiratory disease in feedlots

Bovine Respiratory Disease (BRD) results from a complex, multifactorial interaction of stressors, animal susceptibility, and respiratory pathogens. The infectious agents associated with BRD are ubiquitous among cattle populations. Typically, one or a combination of stressors are necessary to initiate BRD. Prevention of BRD should, therefore, address management procedures to minimise stressors. Administration of vaccines against BRD agents may help reduce the incidence of BRD but is unlikely to eliminate the condition. The effectiveness of antimicrobials in the treatment of BRD depends primarily on early recognition and treatment. The use of antioxidant vitamins, minerals or other agents in the prevention and treatment of BRD warrants further research.     

Prevalence and incidence of bovine trypanosomosis in an agro-pastoral area of southwestern Burkina Faso

The present study was conducted to determine the prevalence and incidence of trypanosomosis and to investigate some factors influencing them in an agro-pastoral area of southwestern Burkina Faso. A total of 363 crossbred cattle (Baoule-zebu peul), which were bred under natural trypanosomosis challenge, were monitored monthly for parasitaemia, packed cell volume (PCV) and serological analyses over 2 years. The parasitological prevalence estimated at the beginning of the survey using the buffy coat technique (BCT) was 7.54%. As much as 66.7% of all trypanosome infections were due to Trypanosoma vivax, 23.8% due to Trypanosoma congolense and 9.5% due to T. vivax/T. congolense mixed infections. The monthly serological incidence varied from 0.29% to 19.29%.The season was the most important factor influencing the serological prevalence and incidence and the animal PCV. The dry hot season is associated with increasing seroprevalences and incidences and consequently a decreasing average of PCV. In addition, an important spatial heterogeneity was observed.     

The resurgence of trypanosomosis in Botswana

No sleeping sickness or nagana cases have been reported in Botswana since 1985. In view of several confirmed clinical cases of nagana and reports of heavy bovine mortality, a parasitological survey was conducted to determine the prevalence of trypanosome infection in cattle in Maun and Shakawe areas of Ngamiland district. Wet blood films, buffy coat and Giemsa-stained thick and thin blood smears were used to detect trypanosomes in animals. Overall,trypanosome infection rate was 15.98%, with 5.94% and 27.29% in Maun and Shakawe respectively. The urgent need to combat trypanosomosis in Ngamiland, particularly in the Shakawe area, is highlighted, and a 3-phase integrated tsetse control strategy for this disease problem is discussed.     

The parasitological and serological prevalence of tsetse-transmitted bovine trypanosomosis in the Eastern Caprivi (Caprivi District, Namibia).

Between August 1995 and June 1997 a survey to determine the distribution of tsetse-transmitted trypanosomosis was conducted in the Eastern Caprivi (Caprivi District, Namibia). A total of 1,481 adult cattle was examined at 33 sampling sites. Direct parasitological diagnostic tests were used and eluted blood spots were screened for the presence of anti-trypanosomal antibodies. Tsetse-transmitted trypanosomal infections were detected in 66 animals (4.5%) from 14 different locations. The parasitological and serological prevalence of trypanosomosis was highest in the Mamili area. Trypanosomosis was virtually absent in the Linyanti/Chobe area and the target barrier along the Kwando River had significantly reduced the prevalence of trypanosomosis in cattle grazing to the east of it. This suggests that anti-trypanosomal antibody prevalence data can be used to evaluate and monitor the effectiveness of tsetse control measures. Survey results suggest that in the Katima Mulilo area, trypanosomal infections were being acquired when cattle grazed along the Zambezi River. Moreover, survey results indicate that tsetse have not been able to establish themselves in the Katima Mulilo area. The parasitological prevalence in a herd and the respective prevalence of anti-trypanosomal antibodies was significantly correlated to the percentage of anaemic animals in that herd. Furthermore, the parasitological prevalence in a herd was positively correlated with the prevalence of anti-trypanosomal antibodies of that herd. It is concluded that the prevalence of anti-trypanosomal antibodies in a herd can be used as an additional indicator of the extent of infection in that particular herd.     

Survey of bovine trypanosomosis in the Kachia Grazing Reserve,Kaduna State,Nigeria

This study assessed the prevalence of trypanosomes in cattle at the Kachia Grazing Reserve (KGR) in March and June 2004 and in February 2005. A total of 1293 cattle blood samples were collected at random. The samples were analysed using the buffy coat technique and Giemsa thin blood films for parasite detection and identification. The effects of herd pen location to watering and grazing point's distances (using the global positioning system (GPS)) were determined and mean Packed cell volume (PCV) assessed. Overall, the detected prevalence of trypanosomosis was 8.4%, much higher than the previous prevalence of 5.3% before the present study was conducted. The prevalences in the months of March, June (2004) and February (2005) were 2.3%, 11.6% and 15.4%, respectively. Increased prevalence was associated with proximity of herd pens to watering point's distances (χ² for linear trend = 4.447, P < 0.05), but no association of herd pens to grazing point distances (χ² = 2.186, P > 0.05); suggesting that hydrological network played an important part in trypanosomosis transmission. The mean PCV of parasitaemic and apparasitaemic cattle were respectively 25.99 ± 1.82% and 29.31 ± 1.70%. The drop in mean PCV was most in 0–1-year age group, 23.47 ± 3.10% and was statistically significant (P < 0.05), suggesting that anaemia was most pronounced in this age group. Factors that may have contributed to the increased prevalence obtained were collapse of control measures and breed susceptibility. Since, Zebu cattle were the predominant breeds in the reserve, the study advocates effective use of insecticide impregnated screens (traps and targets) with community participation in mind for sustainability. If government intervenes through PATTEC ground spraying of insecticides in the reserve is recommended. In addition, chemotherapeutic and chemoprophylaxis should be systematically used to fight the problem of trypanosomosis in the KGR towards improved livestock production.     

A comparative study on the clinical, parasitological and molecular diagnosis of bovine trypanosomosis in Uganda

The clinical, parasitological and molecular diagnosis of bovine trypanosomosis were compared using samples from 250 zebu cattle exposed to natural trypanosome challenge in Uganda. Clinical examination, molecular and parasitological diagnoses detected 184 (73.6%), 96 (38.4%) and 36 (14.4%) as diseased, respectively. The sensitivity and specificity of clinical examination were 87.5% and 35%, and 78 % and 27 % based on molecular and parasitological diagnoses, as gold standards, respectively. Of the 33, 3, 13 and 12 parasitological-positive cattle that had Trypanosoma brucei, Trypanosoma congolense, Trypanosoma vivax or mixed infections, 78 %, 33 %, 84 % and 100 % respectively manifested clinical signs. Of the 24, 89, 12, 3, 6 and 27 cattle detected by molecular diagnosis to have mixed infections, T. brucei, T. vivax, T. congolense forest-, Savannah- and Tsavo-type, 100%, 83%, 91%, 100%, 67% and 81 % had clinical signs, respectively. In conclusion, treatment of cattle based on clinical examination may clear up to 87.5 % or 78 % of the cases that would be positive by either molecular or parasitological diagnosis, respectively. Under field conditions, in the absence of simple and portable diagnostic tools or access to laboratory facilities, veterinarians could rely on clinical diagnosis to screen and treat cases of bovine trypanosomosis presented by farmers before confirmatory diagnosis in diagnostic centres for few unclear cases is sought.     

Development of a decision support system for trypanocidal drug control of bovine trypanosomosis in Africa

During this century livestock production has increased massively through the improved ability to diagnose, treat, control and prevent certain diseases. Despite these advances, disease remains a major constraint to livestock production and welfare throughout the world. In many instances, this is a result of failure to properly apply methods that are already available. TrypsChemo is an expert system that attempts to aid the application of veterinary knowledge to disease management. It has been designed to maximise the effectiveness and cost efficiency of the different trypanocidal drug regimens currently available for prophylaxis and treatment of tsetse-transmitted bovine trypanosomosis in Africa. This paper describes the design of TrypsChemo, the properties of the system, and illustrates how it can be used to support decision making for trypanocidal drug control. The system is currently undergoing a structured evaluation by potential users in Africa.     

Parasitological prevalence of bovine trypanosomosis in Kindo Koisha district,Wollaita zone,south Ethiopia

A cross sectional survey to determine the distribution and prevalence of trypanosomosis was conducted in Kindo Koisha district, in the Wollaita zone in southern Ethiopia. A total of 1 008 adult cattle was examined at eight different localities. Dark field examination of the buffy coat, as well as stained thin blood film examination and packed cell volume (PCV) evaluation were the diagnostic techniques used. The overall prevalence of bovine trypanosomosis was 15 %. Among the positive animals, 108 (71.1%), 43 (28.4%) and 1 (0.6%) were due to Trypanosoma vivax, Trypanosoma congolense and mixed infection (T. vivax and T. congolense), respectively. The infection rate of T. vivax and T. congolense varied significantly (P < 0.01). The mean PCV of the positive and negative animals ranged between 18.3-32.1% and 26.8-33.4%, respectively. The mean PCV of negative animals (28 %) was significantly higher than the mean PCV of positive animals (22.3%) (P < 0.001). There was an inverse association of PCV with the prevalence of trypanosomosis (P > 0.05). The herd average PCV values of each site decreased with increasing proportion of the positive herds of that particular site. Of the diagnostic tests employed, the microhaematocrit buffy coat technique is relatively sensitive and it has an added advantage of indicating the general condition of the animal by haematocrit measurement. In view of the risk of trypanosomosis, a control intervention through the strategic application of appropriate trypanocidal drugs is recommended. A tsetse fly control scheme to reduce host-tsetse fly contact is equally as important as chemotherapy and chemoprophylaxis against trypanosomosis.     

Dyserythropoiesis in animal trypanosomosis

Haemolysis is the most prominent pathogenic cause of the anaemia in trypanosomosis. Haemolytic anaemias are normally accompanied by increased erythropoiesis, reticulocyte response and increase in the mean corpuscular volume of circulating erythrocytes. In trypanosomosis, the anaemia is accompanied by inadequate erythropoiesis. This is suggested by suboptimal reticulocyte response in infected rodents, little or no reticulocyte response in infected ruminants and weak erythrogenic capacity of infected sheep plasma in mice. The mean corpuscular volume increases in the acute phase reaching a peak at 3 to 4 weeks after infection and drops to normal or below normal in the chronic phase; suggesting that erythropoiesis moderately increases in the acute phase but Wanes and becomes completely depressed as the disease progresses into the chronic phase. The causes of the dyserythropoiesis are meanwhile not clear but may be found to be associated with erythroid injury, depressed erythropoietin synthesis and bioactivity or depressed haemoglobin synthesis or their interplay. Extensive studies in these areas are still necessary.