Enhanced survival of rats concurrently infected with Trypanosoma brucei and Strongyloides ratti

The interaction between the blood protozoan parasite, Trypanosoma brucei and the gastrointestinal nematode parasite, Strongyloides ratti was studied in outbred white albino rats. Rats were grouped and given either single infection with T. brucei or S. ratti or concurrently infected with both parasites. Blood parasitaemia and packed cell volume, faecal egg/larva output, adult worm burden and survivability were monitored in order to assess the interactive effects of the infections. All trypanosome-infected rats became parasitaemic within 1 week of infection but surprisingly parasitaemia was higher in the single than concurrently infected group of rats. In addition all animals with single T. brucei infection had died by 14 days after the infection, whereas animals with concurrent infection were still alive by day 28 after the infection when the experiment was terminated. Concurrent infection resulted in significant increase in daily S. ratti egg/larval output in faeces (P < 0.01), but lesser number of adult worms were recovered from the intestine of sacrificed rats on day 8 post-infection. Taken together these results suggest that T. brucei and S. ratti interact in a manner that ameliorates their pathogenic effects resulting in a decrease in the level of parasitaemia and intestinal worm burden and in increased life span of the infected rats. These results differ from the classical immunosuppressive attributes of T. brucei and the results are discussed in the context of the possible immune responses that might have contributed to this outcome and the potential significance of the findings in alternative control method of trypanosomosis.     

Effects of the depletion of CD8(+) T cells and monocytes on the proliferative responses of peripheral blood leucocytes from Trypanosoma evansi-infected sheep

Sheep peripheral blood mononuclear cells and those depleted of CD8(+) T cells and/or monocytes were stimulated with polyclonal mitogens and specific antigens, and analysed by means of cell proliferation assay procedure to examine whether these cell populations are involved in Trypanosoma evansi-induced immunosuppression. The removal of CD8(+) T cells failed to normalize the proliferative responses of peripheral blood mononuclear cells from infected sheep to concanavalin A stimulation while the depletion of monocytes resulted in full and enhanced response, showing that macrophages are mainly responsible for the suppression. Although the depletion of CD8(+) T cells, monocytes or both restored the responses of the cells to lipopolysaccharide stimulation, the responsiveness of the undepleted cells to this mitogen was significantly higher from day 24 post infection (p<0.01). The results were discussed in relation to current known mechanisms of depressed lymphocyte proliferation in tsetse-transmitted African trypanosome infections.     

Porcine trypanosomosis in nigeria: Infections in local and exotic pigs in the Nsukka Area of Anambra State

Summary A twelve-month survey in three Local Government Areas (LGA) in Nsukka zone, Anambra State, Nigeria revealed that out of 150 local and exotic breeds of pig examined, 46 (30·7%) were infected with trypanosomes. Both single and mixed infections ofTrypanosoma brucei andT. congolense were observed. However,T. brucei was the predominant trypanosome encountered. The husbandry system in practice was the most significant factor influencing the prevalence of trypanosomes in the pigs. In addition significantly higher prevalences were recorded during the rainy seasons. Clinical trypanosomosis was encountered in only eight of the 46 positive cases seen, with anaemia, loss of weight and anoestrus being the most important effects associated with these infections. The pathogenic and economic significance of these findings are discussed.

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Resumen Un estudio epidemiológico de 12 meses, sobre tripanosomiasis en cerdos, se llevó a cabo, en tres áreas gubernamentales en Nigeria. El estudio reveló, que de las 150 razas exóticas y locales de cerdos examinados, 46 (30·7 por ciento) se encontraron infectadas con tripanosomas. Se observaron al respecto infecciones únicas y mixtas deTrypanosoma brucei yT. congolense. Sin embargo,T. brucei fue el tripanosoma más observado. Las prácticas de manejo fueron los factores más significativos, sobre la prevalencia de tripanosomiasis en los cerdos estudiados. La prevalencia fue mayor en invierno, encontradose tripanosomiasis clínica en ocho de 46 casos positivos vistos, siendo la anemia, pérdida de peso y anestro, los efectos más importantes asociados con la infección. Se discute la patogénesis e importancia económica de estos hallazgos.

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Résumé Une enquête de 12 mois, dans 3 zones de la région de Nsukka (état d'Anambra au Nigeria) a montré que parmi 150 races ou variétés exotiques ou indigènes de porcs examinées, 46 soit 30, 7 p. 100, étaient infectées de trypanosomes. Des infections uniques ou doubles àTrypanosoma brucei et T. congolense ont été observées, avec prédominance deT. brucei. Le système d'élevage pratiqué s'est révélé le facteur le plus significatif quant à la prévalence des trypanosomes chez cette espèce. De plus, des prévalences significativement plus élevées ont été enregistrées pendant la saison des pluies. Les trypanosomoses cliniques n'ont été constatées que sur 8 des 46 cas positifs. La présence d'anémie, la perte de poids et l'anoestrus ont été les signes les plus importants associés à ces mêmes infections. Les conséquences pathologiques et économiques de ces résultats sont discutées.

     

The effect of dietary protein supplementation on the pathophysiology of Haemonchus contortus infection in West African Dwarf goats

The effect of dietary protein on the pathophysiology of Haemonchus contortus infection in reproducing first pregnancy West African Dwarf (WAD) goats was studied. Eighteen 10-12-month-old pubertal female WAD goats divided into two equal groups were used and confined separately. One group was maintained on high-protein diet (HPD) while the other was maintained on low-protein diet (LPD) from day 1 of pregnancy up to week 6 post-partum. Each animal was infected with 600 infective larvae of H. contortus weekly for 4 weeks and blood collected by jugular venipuncture for the determination of packed cell volume and serum proteins. The results of the study showed that improved protein nutrition significantly enhanced the level of serum albumin (p<0.05). It also significantly lowered the level of serum globulin (p<0.05) that otherwise would be high in haemonchosis. However, improvement in the dietary protein level appeared not to have any effect on the packed cell volume and total serum protein level.     

Adoption and failure rates of vaccinations for disease prevention in chicken farms in Jos,Nigeria

Vaccinations against diseases to prevent disease outbreaks are strategic to disease prevention, but vaccination failures may constitute a challenge in practice. This study was aimed at assessing the adoption and failure rates of vaccinations in 80 chicken farms in Jos, Nigeria. Data were obtained through a structured questionnaire validated by interviews and checking of farm and veterinary records. Vaccination score (0–1) from the vaccination checklist (5 for broilers and 12 for layers) and vaccination procedure score (0–1), based on scored adopted procedures, were calculated for each farm. Vaccine effectiveness was calculated for each vaccine using the odds ratio from the association of frequencies of disease outbreaks in vaccinated and unvaccinated flocks. Farmers used more of imported than local vaccines. Vaccination procedure and vaccination scores did not influence frequencies of disease outbreaks, but vaccination scores tended to non-robustly correlate (r = − 0.89, p > 0.05) with rates of disease outbreak. Vaccination rates were highest against Newcastle disease and infectious bursal disease, and their vaccinations also had the highest effectiveness. There was an association (p = 0.009) between composite vaccination rates and disease outbreaks with 2.1 odds of outbreaks in vaccinated than unvaccinated flocks. Vaccination failures occurred in the use of 11 out of 12 vaccines and the highest failure rate (47.9%) was in vaccination against coccidiosis. Therefore, vaccination failure is a critical factor in poultry vaccination practice within the locality. The adoption of poultry vaccinations needs to be strategised in the context of a national poultry vaccination policy in order to promote effective poultry disease prevention and control.

     

Porcine cerebralTrypanosoma brucei brucei trypanosomiasis

Summary This paper describes the investigation of a disease outbreak among 10 adult pigs in Nsukka, Anambra State, Nigeria. Prior to the investigation one sow died of the disease. Trypanosomes were later detected in the blood of two of the nine pigs subsequently investigated. All the pigs were then treated with deep intramuscular injection of 8 mg/kg diminazene aceturate (Berenil). Thirty six days after treatment a boar and a sow relapsed with signs similar to the ones shown previously. Further examination of their blood and faeces revealed nothing of parasitological significance. Following deteriorating condition and development of nervous signs the boar was salvaged while the sow died of the infection. Brain impression smears taken from both animals during postmortem examination revealed numerous trypanosome parasites identified by morphology and blood incubation infectivity test (BIIT) asTrypanosoma brucei brucei. The clinical and economic significance of the outbreak are discussed.

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Resumen Se describe un brote de tripanosomiasis porcina en cerdos en Nsukka, Estado de Anambra, Nigeria. Antes de la investigación, una cerda murió de la enfermedad. Se detectaron tripanosomas en dos de los nueve cerdos investigados. Todos los cerdos fueron tratados con inyecciones intramusculares de 8 mg/kg de aceturato de diminazene (Berenil). Treinta y seis días después del tratamiento, un macho y una henbra desarrollaron una sintomatología similar a la vista previamente. Exámenes subsecuentes de sangre y heces no revelaron nada de significancia parasitológica. Después del deterioro de las condiciones físcias y metabólicas y el desarrollo de síntomas nerviosos, el macho se sacrificó mientras que la hembra murió. Las impresiones de cerebro revelaron numerosos tripanosomas, los cuales fueron identificados por morfología y mediante la prueba de incubación de infectividad, comoTrypanosoma brucei brucei. Se discute la importancia económica del brote.

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Résumé Cet article décrit l'enquête menée sur un foyer pathologique concernant dix porcs adultes à Nsukka, Etat d'Anambra au Nigéria. Prélablement à l'enquête proprement dite, une truie était morte de trypanosomose. Ultérieurement des trypanosomes furent trouvés dans le sang de deux des neuf porcs traités par une injection intramusculaire profonde d'acéturate de diminazéne (Bérénil) à la dose de 8 mg/kg. Trente six jours après le traitement, un verrat et une truie firent une rechute avec des signes identiques à ceux déjà constatés. Des examens ultérieurs du sang et des fèces ne revélèrent aucun parasite. A la suite d'une aggravation de leur état général et de l'apparition de signes nerveux, le verrat guérit mais la truie succomba de l'infection naturelle. Les frottis par décalque du cerveau prélevés sur les 2 animaux lors d'une autopsie, ont révélé de nombreux trypanosomes. Par leur morphologie et par le test d'infectivité du sang, après incubation, ceux-ci furent identifiés comme étantTrypanosoma brucei brucei. La signification clinique et économique de ce foyer fait l'objet d'une discussion.

     

Murine model study of the practical implication of trypanosome-induced immunosuppression in vaccine-based disease control programmes

The relevance of trypanosome-induced immunosuppression in relation to the efficacy of vaccine-induced immunity was studied in mice. Mice were immunised with crude Trichinella spiralis muscle larvae homogenate vaccine and infected with T. spiralis and/or Trypanosoma brucei. Vaccination significantly decreased adult worm burden (p<0. 05) and accelerated worm expulsion in mice infected with T. spiralis only. T. brucei superinfection resulted in monocytosis, suppressed eosinophilia, significant decrease in PCV (p<0.001), higher numbers of adult worms (p<0.001) and failure to expel all adult worms by Day 12 post infection (p.i.). Regardless, they produced anti-Trichinella IgG(1) responses similar to those of the vaccinated non-T. brucei-infected group. T. brucei also suppressed the proliferative responses of spleen cells to stimulation with Con A and T. spiralis antigen, and induced strong production of interferon-gamma (IFN-gamma) in culture supernatants of antigen stimulated spleen and mesenteric lymph node cells. Interleukin-5 (IL-5) production was suppressed by T. brucei in supernatants of Con A- and antigen-stimulated spleen cells. It was concluded that trypanosome infections and the associated immunosuppression are of great practical significance in trypanosome endemic areas, especially with regards to disease control programmes involving vaccine-induced herd immunity.     

Drug resistance in pathogenic African trypanosomes: what hopes for the future?

Trypanosomosis is a serious threat to both man and animals mostly in Africa. Although the first pathogenic trypanosome was discovered over a hundred years ago, there is still no prospect for effective control or eradication of the disease through the development and use of vaccines because of the phenomenon of antigenic variation. Control continues to rely heavily on chemotherapy and vector control strategies. This therapy and prophylaxis depends on the use of drugs which, apart from having been developed over 5 decades ago, suffer from such limitations as toxicity and with their continued use, drug resistance. Resistance to currently used drugs is a serious problem in most fields of anti-microbial chemotherapy, particularly in the case of trypanosomosis where resistance and cross-resistance in animals and man have been developing rapidly. The frequently and widely reported decreasing efficiency of available trypanocides, difficulties of sustaining tsetse control and little hope that a conventional, anti-trypanosome vaccine will be produced in the near future, increase the imperative need for new drugs and alternative effective ways for the control of trypanosomosis. This review examines aspects of drug resistance in pathogenic trypanosomes, measures to minimise it, areas of future research in new drug targets and alternative control strategies. Based on these, it is our opinion that for now the management and control of trypanosomosis will continue to depend on proper usage of the few available trypanocides, especially strategic deployment of the sanative drugs in order to reduce the development of drug resistance, in addition to the continued use of environmentally friendly vector control programmes such tsetse trapping.