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.     

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.     

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.     

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%).     

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.     

The distribution and epidemiology of bovine trypanosomosis in Malawi

A survey to update the distribution and clarify the epidemiology of bovine trypanosomosis in Malawi was conducted between 1995-97. Use was made of parasitological and serological (anti-trypanosomal antibody-detection Enzyme-Linked Immunosorbent Assay (ELISA) diagnostic methods. Trypanosomal infections were detected in cattle sampled adjacent to known tsetse foci. The distribution of cattle with anti-trypanosomal antibodies indicated that the distribution of bovine trypanosomosis was more widespread than the parasitological prevalence data suggested. This is attributed to the seasonal movement of tsetse (mainly Glossina morsitans morsitans and G. pallidipes) from its prime habitat and the presence of localized foci of G. brevipalpis. The odour-baited, insecticide-treated, target barriers along the edge of Kasungu National Park and the Nkhotakota Game Reserve appeared to be effective in preventing tsetse from moving outside the game areas and contacting cattle. The anti-trypanosomal antibody-detection ELISA proved to be a useful tool in establishing the distribution of bovine trypanosomosis. Moreover, the distribution and prevalence of cattle with anti-trypanosomal antibodies was instrumental in clarifying the epidemiology of bovine trypanosomosis in Malawi. The anti-trypanosomal antibody-detection ELISA had high sensitivity in detecting Trypanosoma congolense infections. In parasitologically negative animals, the average packed cell volume was higher in those that had no anti-trypanosomal antibodies. The packed cell volume decreased with increasing antibody titre.     

Seasonal prevalence of bovine trypanosomosis in a tsetse-infested zone and a tsetse-free zone of the Amhara Region, north-west Ethiopia

During a period of four consecutive years, trypanosomosis surveys were conducted in a tsetse-infested and tsetse-free area of the Amhara Region of north-west Ethiopia. In each study area randomly selected communal cattle were sampled and their blood was investigated using parasitological diagnostic methods. At the same time the population of biting flies was sampled. The monthly average prevalence of trypanosome infections in cattle did not differ significantly between study areas. In both study areas, the prevalence of trypanosome infections was highest during the long rainy season. Trypanosome infections were mainly due to Trypanosoma vivax and they significantly reduced the average packed cell volume and the body condition of the animals. The monthly prevalence of infection was correlated with the density of biting flies, such as Tabanidae and Stomoxys spp., in the preceding month suggesting an important role of mechanical transmission in the epidemiology of trypanosomosis in both areas.     

Survey of ixodid ticks and two tick-borne pathogens in African buffaloes, Syncerus caffer, from the Caprivi Strip, Namibia

A capture operation to ascertain health status in free-ranging buffaloes from six different areas in the Caprivi Strip in the northeast corner of Namibia was conducted in October 2009. Basic information on the ticks and tick-borne pathogens normally found in wildlife from this area are scarce. The objective of this study was to assess the host status of African buffaloes, Syncerus caffer, for ixodid ticks and two selected tick-borne pathogens in the Caprivi Strip, a key area bordering Angola, Zambia, Botswana, and Zimbabwe. Four different tick species have been identified among the 233 collected specimens, and, of 95 tested buffaloes, 54 (57%) were positive for Theileria parva, whereas only 3 (3%) showed evidence of being infected with Ehrlichia ruminantium.     

Comparative diagnosis of parasitological,serological, and molecular tests in dourine-suspected horses

Study on comparative sensitivity of parasitological, serological, and molecular tests on 237 horses originating from two dourine-suspected districts of Arsi-Bale highlands of Ethiopia was conducted to determine the prevalence of the disease and degree of agreement of the diagnostic tests. Accordingly, the prevalence of the disease was found to be 4.6%, 36.7%, and 47.6% by parasitological Woo test, RoTat 1.2 and 18S PCR tests, respectively. The seroprevalence of the disease was 27.6% in CATT/Trypanosoma evansi test. In Ethiopia, it was for the first time that trypanosomes from dourine suspected horses were demonstrated in 4.6% of the animals using Woo test. The findings of the present study disclosed that dourine is highly prevalent and one of the major diseases of horses in the area. There was no statistically significant difference (P > 0.05) in prevalence of the disease between districts, sexes, and age groups of the animals. However, there was a statistically significant difference (P < 0.05) in the prevalence of the disease between emaciated and animals with good body condition. Assessment of the degree of agreement of the diagnostic tests employed revealed low to fair ( k = 0.1 - 0.4 ) \left( {k = 0.{1} - 0.{4}} \right) with significantly higher sensitivity by PCR than other tests.     

A serological survey on the prevalence of infectious bovine rhinotracheitis in Buckinghamshire, Berkshire and Oxfordshire.

Of the 2368 cattle sera from herds in Buckinghamshire, Berkshire and Oxfordshire examined for infectious bovine rhinotracheitis antibody by an indirect haemagglutination test, 162 (6.8 per cent) proved positive. Positive titres were more prevalent in older cows and they tended to show higher titres. There was little evidence of infection in the bulls tested. The percentage of positive animals in Berkshire and Oxfordshire was 4.7 compared with 10.5 in Buckinghamshire. The infection was not known to be associated with any clinical disease.     

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.     

Adaptation and validation of antibody-ELISA using dried blood spots on filter paper for epidemiological surveys of tsetse-transmitted trypanosomosis in cattle

The indirect enzyme-linked immunosorbent assay (ELISA) for the detection of anti-trypanosomal antibodies in bovine serum was adapted for use with dried blood spots on filter paper.

Absorbance (450 nm) results for samples were expressed as percent positivity, i.e. percentage of the median absorbance result of four replicates of the strong positive control serum.

The antibody-ELISA was evaluated in Zambia for use in epidemiological surveys of the prevalence of tsetse-transmitted bovine trypanosomosis. Known negative samples (sera, n=209; blood spots, n=466) were obtained from cattle from closed herds in tsetse-free areas close to Lusaka. Known positive samples (sera, n=367; blood spots, n=278) were obtained from cattle in Zambia's Central, Lusaka and Eastern Provinces, diagnosed as being infected with Trypanosoma brucei, T. congolense, or T. vivax using the phase-contrast buffy-coat technique or Giemsa-stained thick and thin blood smears. For sera (at a cut-off value of 23.0% positivity) sensitivity and specificity were 86.1 and 95.2%, respectively. For bloodspots (at a cut-off value of 18.8% positivity) sensitivity and specificity were 96.8 and 95.7%, respectively. The implications of persistence of antibodies following treatment or self-cure are discussed.     

An outbreak of contagious bovine pleuropneumonia in the Owambo Mangetti area of South West Africa/Namibia: microbiological, immunofluorescent, pathological and serological findings

An outbreak of contagious bovine pleuropneumonia (CBPP) in the Owambo Mangetti area of South West Africa/Namibia in 1982 led to the slaughter of 3,153 cattle. The lungs of 266 of these animals were scrutinized for gross lesions of CBPP and samples of lung tissue, sequestral contents or pleural fluid were submitted to the Veterinary Research Institute (VRI), Onderstepoort for microbiological, immunofluorescent and pathological examination. Immunofluorescence proved to be the most successful method of diagnosis producing 96% of positives, while mycoplasma isolations were only positive in 64% of the 55 specimens processed in parallel. This clearly demonstrated the value of the former technique in the accurate as well as rapid diagnosis of CBPP. The impression smear technique employed, using Eriochrome black counterstaining proved most satisfactory and easy to interpret. The isolation of M. mycoides was influenced by the transit times and temperature of the samples on arrival at the VRI. No pathogenic bacteria were found in routine aerobic bacterial cultures from 27 of the samples submitted. Complement fixing antibodies were present in the sera of 16 cattle and titres varied between 10 and 320. Animals in which antibodies were absent included those with early lung lesions and some with sequestra.     

Apparent prevalence of dourine in the Khomas region of Namibia

A 15-year record of the results of horse sera from the Khomas region of Namibia tested by the complement fixation test for dourine at the Central Veterinary Laboratory in Windhoek before clearing the respective animals for export and competitive sport were subjected to statistical analysis. The range of percentage positive, taken as the apparent prevalence of dourine for the region, during the period of study, was 0-29.09%; the average regional level of apparent prevalence was 8.33%. These figures were thought to be lower than the real situation due to some bias in the sampling criteria. For more accurate results, the more reliable enzyme-linked immunosorbent assay techniques are recommended for use in sero-surveys for dourine in Khomas and other regions of Namibia to provide a basis for development of effective control strategies against the disease.     

A parasitological, molecular and serological survey of Hepatozoon canis infection in dogs around the Aegean coast of Turkey

Canine hepatozoonosis is caused by the tick-borne protozoon Hepatozoon spp. The prevalence of the infection in the Aegean coast of Turkey was investigated by examination of blood smear parasitology and polymerase chain reaction (PCR) using blood samples from 349 dogs collected from Central Aydin, Kusadasi, Selcuk, Central Manisa, Bodrum and Marmaris within the Aegean coast of Turkey. The indirect fluorescent antibody test (IFAT) for the detection of Hepatozoon canis antibodies was also used to detect the exposure rate to H. canis. PCR amplifying a 666bp fragment of 18S rRNA gene of Hepatozoon spp. was used in the epidemiological survey. The prevalence of Hepatozoon spp. infection was 10.6% by blood smear parasitology and 25.8% by PCR. IFAT revealed that 36.8% of serum samples were positive for antibodies reactive with Hepatozoon spp. The PCR products of 18S rRNA gene of Hepatozoon spp. isolated from six infected dogs, one isolate originating from each of the six different locations, were sequenced. The results of sequence analysis indicate that they are closely related to Indian and Japanese isolates of H. canis. This is the first epidemiological study on the prevalence of H. canis infection in the dog, in Turkey.     

Quantitative correlation of parasitological and serological techniques for the diagnosis of Trypanosoma congolense infection in cattle

A comparison was made between serological and parasitological techniques for the diagnosis of bovine trypanosomiasis in Zambia. Overall sero-prevalence rates as determined by IFAT and ELISA were respectively 2.7-fold and 2.9-fold greater then the percentage of samples found positive with the dark ground/phase contrast buffy coat technique (DG). The results obtained by the two serological techniques were found to be closely correlated (94.2%) agreement) and titres obtained by ELISA tended to be slightly higher than those obtained by IFAT. Linear regression analysis of the results obtained by the IFAT and DG techniques revealed a highly significant correlation. This finding would permit the use of only one of the techniques in an epidemiological survey and to extrapolate the results from the regression line.     

Quantitative correlation of parasitological and serological techniques for the diagnosis of Trypanosoma congolense infection in cattle

Summary

A comparison was made between serological and parasitological techniques for the diagnosis of bovine trypanosomiasis in Zambia. Overall sero‐prevalence rates as determined by IFAT and ELISA were respectively 2.7‐fold and 2.9‐fold greater then the percentage of samples found positive with the dark ground/phase contrast buffy coat technique (DG). The results obtained by the two serological techniques were found to be closely correlated (94.2% agreement) and titres obtained by ELISA tended to be slightly higher than those obtained by IFAT. Linear regression analysis of the results obtained by the IFAT and DG techniques revealed a highly significant correlation. This finding would permit the use of only one of the techniques in an epidemiological survey and to extrapolate the results from the regression line.     

An update of the bovine trypanosomosis situation at the edge of Hluhiuwe-Imfolozi Park, Kwazulu-Natal Province, South Africa

To obtain updated data on and assess the contribution of trypanosomosis to the disease burden of cattle kept at the edge of the Hluhluwe-iMfolozi Park, a survey was conducted at Mvutshini Dip. Use was made of a purposeful sampling strategy by restricting sampling to animals that the livestock owner considered to be in poor condition. Of a total of 76 blood samples collected, 26 were parasitologically positive and 46 were positive on PCR/RFLP. Almost all infections were due to Trypanosoma congolense savannah subgroup. A total of 63 animals had a PCV < or = 24% and were considered to be anaemic. Results from the survey show that trypanosome infections contribute significantly to the overall burden of disease in the area. Further research is required to develop appropriate control methods.     

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.