Interference between drug-resistant and drug-sensitive stocks of Trypanosoma congolense in goats

A study was undertaken in goats to investigate the ability of two unrelated stocks of Trypanosoma congolense, one of which is highly sensitive to isometamidium chloride and one which is drug-resistant, to become established in the presence of an existing infection with the other stock. The goats, which were initially infected with the sensitive strain and were then challenged with the resistant strain, were cured by treatment at 0.1 mg kg-1 isometamidium, indicating that the resistant stock did not establish an infection. Goats initially infected with the resistant stock, which were then challenged with the sensitive stock, experienced temporary remission of infection followed by relapse after treatment at 0.1 mg kg-1 isometamidium. In contrast, the goat infected only with the resistant stock remained parasitaemic following treatment at 0.1 mg kg-1. This suggests that superinfection with the sensitive stock resulted in the establishment of infection, which suppressed the resistant stock to below the limit of detection of the method used. These observations suggest that isometamidium-resistant stocks may be less viable than sensitive strains, and could explain the relative scarcity of isometamidium resistant in the field.     

Changes in levels of transaminases in goats experimentally infected with Trypanosoma congolense.

Goats were experimentally infected with Trypanosoma congolense and then treated with Berenil after 9 days of infection. The infection produced increases in glutamate oxalacetate transaminase (GOT) and glutamate pyruvic transaminase (GPT) values. Mean GOT values in infected West African dwarf goats were generally lower than in infected Red Sokoto goats. Treatment with Berenil did not produce any significant effect on their levels probably because of the relapse infection recorded in this study.     

Trypanosomes in the lymph nodes of cattle and sheep infected with Trypanosoma congolense

The prefemoral lymph nodes of two calves and a sheep infected with a stock of Trypanosoma congolense transmitted by Glossina morsitans were examined histologically for the presence of trypanosomes. Ten days after infection trypanosomes were found in the subcapsular sinuses of the nodes of a calf and the sheep but parasites were absent from the blood at this time. Trypanosomes were also detected in the prefemeral lymph node of the other calf on examination 30 days after infection, when parasites were also present in the blood. These observations provide further evidence that extravascular foci of trypanosomes develop in infections with T congolense and indicate that it should not be regarded as a strict plasma parasite.     

Response of Trypanosoma congolense in goats to single and double treatment with diminazene aceturate.

Diminazene aceturate is one of a limited number of compounds currently marketed for treatment of trypanosomiasis in cattle, sheep and goats. The pharmacokinetics of the compound in goats suggest that double treatment with diminazene aceturate might enhance the compound's therapeutic activity. A study was therefore conducted in goats using two clones of Trypanosoma congolense, IL 3274 and IL 1180, which were previously shown to be resistant and sensitive, respectively, to single treatment with diminazene aceturate. The results indicated that, as compared to single treatment, double treatment with diminazene aceturate at a dose of 7.2 mg kg-1 bodyweight, at either eight or 24 hour intervals, did not greatly enhance the therapeutic activity of the drug. Furthermore, treatment with the same drug dose eliminated infections with T congolense IL 3274 when treatment was administered 24 hours after infected Glossina morsitans centralis had fed, but failed to do so if treatment was delayed until after goats were detected to be parasitaemic. This suggests that failure of T congolense IL 3274 to respond to treatment with diminazene may not be due to drug resistance per se.     

Village production of West African Dwarf goats and sheep in Nigeria

Results from a 41 month study of West African Dwarf goats and sheep under village conditions in south-west Nigeria are reported. Even at a very low level of management these trypanosomiasis-tolerant animals produced 2.01 kids or 1.51 lambs per dam per year. Mortality of young particularly kids and low growth rates limit production. Of these mortality is probably the first constraint to increased productivity and profitability. Control of peste des petits ruminants appears to significantly reduce mortality and should stimulate the further development of this production system.     

Prevalence of antibodies to Dermatophilus congolensis in sheep and goats in Nigeria

Summary

A serological survey on dermatophilosis was carried out amongst sheep and goats in Kaduna State of Nigeria. Sera were‐obtained from slaughter animals and from sheep kept on an isolated ranch. The percentage of seropositive animals was 28.0 in slaughter sheep, 0.0 in sheep kept on the ranch, and 23.2 in slaughter goats. The high prevalence of D. congolensis antibodies among small ruminants compares well with the level of prevalence reported of cattle and calls for a concerted government effort for the control of the disease.     

Prevalence of antibodies to Dermatophilus congolensis in sheep and goats in Nigeria

A serological survey on dermatophilosis was carried out amongst sheep and goats in Kaduna State of Nigeria. Sera were obtained from slaughter animals and from sheep kept on an isolated ranch. The percentage of seropositive animals was 28.0 in slaughter sheep, 0.0 in sheep kept on the ranch, and 23.2 in slaughter goats. The high prevalence of D. congolensis antibodies among small ruminants compares well with the level of prevalence reported of cattle of cattle and calls for a concerted government effort for the control of the disease.     

Prevalence of Sarcocystis species in sheep and goats in northern Nigeria.

Tissue samples comprising the oesophagus and diaphragm were collected from 400 sheep and 400 goats slaughtered at the abattoirs in the study area. Out of this number, 36 were positive for Sarcocystis cysts (sarcocysts) in sheep and 56 in goats. The sarcocysts in sheep measured 35.7 to 500 microns lengthwise and the cyst-wall 2.4 microns. They were identified to be Sarcocystis tenella. The cysts in goats measured 98 to 700 microns and the cyst-wall 2.7 microns. They were identified to be Sarcocystis capracanis. In both animals species, the sarcocysts were more frequent in the oesophagus than in the diaphragm. All sarcocysts seen were microscopic.     

Role of the chancre in induction of immunity to tsetse-transmitted Trypanosoma (Nannomonas) congolense in goats

Local skin reactions (chancres) developed in goats at the sites of deposition, by tsetse flies, of metacyclics of Trypanosoma congolense. The chancres developed much faster and were more pronounced when ten infected tsetse were allowed to feed on a spot as compared to only one fly per spot. The initial host cellular reaction in the chancre was predominantly polymorphonuclear, followed at the peak of development of the chancre by a predominantly lymphoblastic and plasmacytic reaction. Trypanosomes were found in various stages of division as well as degeneration in chancre biopsies taken at various days post-infection (p.i.). Most of the trypanosomes recovered from the chancre tissue fluid were found to bear the same variable surface glycoprotein (VSG) epitopes as the corresponding metacyclics for as long as 13 days p.i., as revealed by indirect immunofluorescence using mouse anti-metacyclic VSG hyperimmune sera and monoclonal antibodies. Immunization of goats with metacyclic trypanosomes, by exposure to infected tsetse bites followed by treatment of the infected goats on day 13 p.i., gave rise to the development of protection to homologous tsetse-transmitted challenge, whilst immunization by intravenous inoculation of the metacyclics did not induce such protection. Chancre formation would thus appear to be vital for the induction of comprehensive immune recognition of the metacyclic variable antigen repertoire deposited in the skin by infected tsetse, and hence development of protective immunity.     

Comparative study of milk compositions of cattle,sheep and goats in Nigeria

Variations in the milk composition of Nigerian cattle, sheep and goats (Bunaji, Yankasa and Red Sokoto breeds, respectively), as well as residual phenotypic correlations between the milk constituents, were investigated. Results indicated that sheep and goats differed significantly (P < 0.05) from cattle in all constituents except protein percentage, which averaged 5.43%, 5.43% and 5.49%, respectively. Caprine milk contained the highest percentages of fat (5.80%), total solids (15.37%) and ash (0.77%), and bovine milk contained the least percentages of fat (0.68%) and lactose (1.84%). Overall, the milk compositions of sheep and goats were very similar as they were not statistically different from each other (P > 0.05). Residual phenotypic correlations between the milk constituents revealed highly significant (P < 0.01) and positive relationships between total solids and solids‐not‐fat (0.97 and 0.98 in cattle and sheep, respectively). All other correlations were positive in cattle (ranging from 0.12 to 0.77), except between protein and total solids (?0.44) and protein and solids‐not‐fat (?0.64). Multiple linear regression equations were fitted to predict the percentages of protein and fat. It was demonstrated that the protein percentage could be predicted from total solids and solids‐not‐fat with the highest accuracy of 94%, 86% and 82% in cattle, sheep and goats, respectively. On the other hand, the accuracy of prediction of fat percentage was very low in all the species (R² = 0.01, 0.3 and 0.37 in cattle, sheep and goats, respectively).     

Trypanosoma congolense infection in two dogs

Trypanosomiasis, caused by Trypanosoma congolense, was diagnosed for the first time in Israel in two boxer dogs imported from Kenya. The dogs developed clinical signs two days after arrival and succumbed to the disease within four days. The major clinical and clinicopathological findings included anaemia, haemorrhages, lymphadenomegaly, hepatosplenomegaly and neurological signs. Histopathology showed lymphocytic-plasmacytic infiltration in the skin, brain, meninges, kidney and liver.     

The pathogenesis of anaemia in goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei: use of the myeloid:erythroid ratio

The present study examined the development of anaemia in Small East African goats experimentally infected with Trypanosoma congolense or Trypanosoma brucei. Experimental goats received a primary trypanosome challenge on day 0, treated with diminazene aceturate on day 49 and received a secondary trypanosome challenge on day 77 of the 136-day experiment. Both primary and secondary challenges were characterised by reduced peripheral erythrocyte counts, fall in packed cell volume (PCV), hypohaemoglobinaemia and reductions in the myeloid:erythroid ratios (M:E) compared with the uninfected goats. The progressive reduction in the M:E ratios denoted increased erythrogenesis in response to increased destruction of erythrocytes in blood by infecting trypanosomes or their products. The more rapid fall in M:E ratio in T. congolense infections shows that this parasite causes more severe clinical pathological effects in goats than T. brucei.     

Susceptibility of West African Dwarf goats and WAD x Saanen crosses to experimental infection with Trypanosoma congolense

West African Dwarf goats (WADs) and their Saanen crosses were experimentally infected with Trypanosoma congolense. No significant differences were found between trypanosome parasitaemia and antibody response of the crossbred and WAD goats. Neither the WAD goats nor the Saanen crosses were able to control the drop in PCV following trypanosome infection. The level of anaemia caused by the trypanosome infection was similar in the two breeds during the trial. Based on these findings, no difference in tolerance or susceptibility to T. congolense could be demonstrated between the WAD goats and their Saanen crosses. Although the weight of all goats increased during the trial, the crosses gained significantly more weight than the WAD goats. The trypanosome infection reduced the growth rate of both breeds, but this reduction was not statistically significant. Crossbreeding trypanotolerant WADs with trypanosusceptible Saanen goats might, therefore, be an effective means of increasing productivity.