Protective efficacy of isometamidium chloride and diminazene aceturate against natural Trypanosoma brucei, Trypanosoma congolense and Trypanosoma vivax infections in cattle under a suppressed tsetse population in Uganda.

The protective efficacy of isometamidium chloride (ISMM) and diminazene aceturate (DIM) against Trypanosoma brucei, Trypanosoma congolense and Trypanosoma vivax infections in cattle under a suppressed tsetse population was assessed in southeast Uganda. A total of 66 and 57 trypanosome-infected cattle were treated with ISMM and DIM, respectively together with 177 trypanosome-free animals not treated were followed for 12 months, checked every 4 weeks. There was no statistical difference in the mean time to infection with any trypanosome species in animals treated with ISMM or DIM. However, the mean time to trypanosome infection was significantly longer for treated animals than controls. The mean time to infection with each of the three trypanosome species differed significantly, with the average time to T. vivax infection the lowest, followed by T. congolense and then T. brucei. The protective efficacy of DIM was as good as that of ISMM; implying curative treatments against trypanosomosis are sufficient for combination with tsetse control. Isometamidium chloride or DIM had the highest impact on T. brucei and T. congolense infections in cattle.

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.

Occurrence of concurrent trypanosomosis, theileriosis, anaplasmosis and helminthosis in Friesian, Zebu and Sahiwal cattle in Uganda.

An epidemiological investigation was conducted on farms in Tororo and Soroti districts of Uganda from January to February 2000 to determine the cause of reported persistent mortality of cattle. Blood and faecal material of 98 cattle comprising of 33 Friesians, 58 Zebu and 7 Sahiwal were examined. Results revealed that seven (7.1 %) cattle had trypanosome infection, mainly due to Trypanosoma vivax and T. brucei, 17 (17.3%) Fasciola infection, 28 (28.6%) gastrointestinal nematode infection, 33 (33.7%) Theileria sp. infection and 13 (13.3%) Anaplasma marginale infection. Mixed infections were detected in 30%, 20.6% and 43 % of the Friesian, Zebu and Sahiwal cattle respectively. Anaemia (PCV < 25) was detected in 24%, 19% and 14% of the Friesian, Zebu and Sahiwal cattle respectively. Persistent mortality of cattle on these farms could have been due to either single or mixed parasitic infections probably exacerbated by malnutrition.

Comparative evaluation of the antibody-detection ELISA technique using microplates precoated with denatured crude antigens from Trypanosoma congolense or Trypanosoma vivax.

Two FAO/IAEA indirect enzyme-linked immunosorbent assays (ELISA), which use microplates precoated with denatured crude Trypanosoma congolense or Trypanosoma vivax antigen for detecting anti-trypanosomal antibodies in bovine sera, were evaluated for their sensitivity, specificity and positive and negative predictive values, using 320 Ugandan field samples (known negative sera, n = 80; known positive sera, n = 80; cattle herds where control of tsetse and trypanosomosis was practiced, n = 80; and cattle herds where there was no such control, n = 80). Cut-off points of 30% and 25% positivity were determined for the T. congolense and T. vivax assays, respectively, using a modified ROC (receiver operating characteristic) analysis. The T. congolense assay had estimated diagnostic sensitivity and specificity of 63.7% and 57.5%, respectively, while the T. vivax assay had estimated diagnostic sensitivity and specificity of 81.3% and 81.3%, respectively. The two assays conducted in parallel had estimated diagnostic sensitivity and specificity of 82.5% and 88.7%, respectively. Using the sera from the cattle in the area with control (detected prevalence of trypanosomosis 0%), both the T. congolense and T. vivax assays had negative and positive predictive values of 100% and 0%, respectively. Using the sera from the cattle in the area without control (detected prevalence of trypanosomosis 15%), the T. congolense assay had negative and positive predictive values of 91% and 33%, respectively, and the T. vivax assay had negative and positive predictive values of 93% and 27%, respectively. The T. congolense assay was in fair agreement with the buffy coat technique (BCT) (kappa = 0.25), while the T. vivax assay was in substantial agreement with the BCT (kappa = 0.625), and both assays conducted in parallel were in substantial agreement with the BCT (kappa = 0.708). Both assays were found to be proficient and suitable for the diagnosis of bovine trypanosomosis, especially when used in parallel.

Sustainability of tsetse control by subsequent treatment of 10% of a previously treated Ugandan cattle population with 1% w/v deltamethrin.

This study was conducted in Masaba and Masafu Sub-counties, Busia District, Uganda to assess the effect on the tsetse fly population of first treating all cattle with 1% w/v deltamethrin pour-on for a few months, followed by treating 10% of the cattle population. Treatment of all cattle for 6 months resulted in a significant reduction in the density of tsetse flies from 6.3 to 0.1 flies/trap/day (FTD), a 98.4% reduction. During the same period, the point prevalence of bovine trypanosomosis dropped from 37.7% to 2.9% (a 92.3% reduction). Treatment was resumed six months later, but this time only 10% of the cattle population received the pour-on treatment at three week intervals for a period of one year. This treatment maintained the tsetse fly density between 0 and 0.5 FTD and the prevalence of bovine trypanosomosis generally remained below 10%. In conclusion, under the local prevailing conditions, treatment of all communally grazed cattle with deltamethrin pour-on effectively suppressed the Glossina fuscipes fuscipes population. However, subsequent treatment of 10% of the cattle probably failed to control the tsetse fly population at a level sufficient to reduce trypanosomosis to acceptable levels.