Evaluation of a field test for trypanotolerance in young N'Dama cattle

Evaluates components of a short term test for trypanotolerance criteria in N'Dama post-weaners exposed to a medium natural trypanosome challenge in Gabon; compares the effectiveness of different measures of control of development of anaemia; and measures the post-test recovery of packed red cell volume (PCV) values following treatment with a trypanocidal drug

Measurement of trypanotolerance criteria and their effect on reproductive performance of N'Dama cattle

Evaluates in detail how environmental and stress factorts affect trypanosome infection in N'Dama cows and their calves, the linkages with curative drug treatment given under the management regime prevailing, the linkages with anaemia control as measured by packed red cell volume (PCV), and the resultant influences on animal performance. Major findings were that over the period from calf birth to weaning, while calves and their dams grazing together had similar numbers of trypanosome infections detected, the Trypanosoma vivax : T. congolense rations were very different: 1:0.7 in calves and 1:2.8 in cows. This indicated that some ability to control the development of parasitaemia following T. vivax infection might be being acquired, from weaning onwards. Table 1 summarizes the data on trypanosome infection, curative drug treatment, PCV value and performance trait levels in the 458 pre-weaner calves, the 458 lactating cows and the 1028 cow-year reproduction records available over the 5-year period. These are the actual overall infection rates recorded, the levels of curative drug treatments required and the PCV values, calf growth and cow calving rates achieved

Aspects of trypanotolerance and associations with growth rate in post-weaner N'Dama cattle under high trypanosomiasis risk

A study conducted to find out the ability of N'Dama cattle to control parasitaemia and anaemia at a ranch in Gabon. Examines the effect of parasitaemia on daily liveweight change

Glossina fusca group tsetse as vectors of cattle trypanosomiasis in Gabon and Zaire

The significance of Glossina fusca group tsetse flies as vectors of cattle trypanosomiasis was examined using biconical traps to survey tsetse populations at one site in Gabon and two sites in Zaire. Mean trypanosome infection rates in G. tabaniformis Westwood over the study period ranged from 8.9 - 17.7 percent at the two sites. The mean infection rate in G. nashi Potts was 6 percent. Up to 49 percent of bloodmeals of G. tabaniformis were from cattle. Trypanosome prevalence in cattle where G. tabaniformis appeared to be the main vector was 9.5 percent and 5.4 percent at the Mushie and OGAPROV ranches respectively. A highly significant positive correlation was found between tsetse challenge and trypanosome prevalence in N'Dama cattle across sites. Tsetse challenge was defined as the product of tsetse relative densities, trypanosome infection rates in the flies and the proportion of feeds taken by them from cattle. Thus G. tabaniformis can be an important vector of pathogenic Trypanosoma species in cattle

Development of a viral biopesticide for the control of the Guatemala potato tuber moth Tecia solanivora

The Guatemala potato tuber moth Tecia solanivora (Povolny) (Lep. Gelechiidae) is an invasive species from Mesoamerica that has considerably extended its distribution area in recent decades. While this species is considered to be a major potato pest in Venezuela, Colombia, and Ecuador, currently no specific control methods are available for farmers. To address this issue we developed a biopesticide formulation to be used in integrated pest management of T. solanivora, following three steps. First, search for entomopathogenic viruses were carried out through extensive bioprospections in 12 countries worldwide. As a result, new Phthorimaea operculella granulovirus (PhopGV) isolates were found in T. solanivora and five other gelechid species. Second, twenty PhopGV isolates, including both previously known and newly found isolates, were genetically and/or biologically characterized in order to choose the best candidate for a biopesticide formulation. Sequence data were obtained for the ecdysteroid UDP-glucosyltransferase (egt) gene, a single copy gene known to play a role in pathogenicity. Three different sizes (1086, 1305 and 1353 bp) of egt were found among the virus isolates analyzed. Unexpectedly, no obvious correlation between egt size and pathogenicity was found. Bioassays on T. solanivora neonates showed a maximum of a 14-fold difference in pathogenicity among the eight PhopGV isolates tested. The most pathogenic PhopGV isolate, JLZ9f, had a medium lethal concentration (LC50) of 10 viral occlusion bodies per square mm of consumed tuber skin. Third, we tested biopesticide dust formulations by mixing a dry carrier (calcium carbonate) with different adjuvants (magnesium chloride or an optical brightener or soya lecithin) and different specific amounts of JLZ9f. During laboratory experiments, satisfactory control of the pest (>98% larva mortality compared to untreated control) was achieved with a formulation containing 10 macerated JLZ9f-dead T. solanivora larvae per kg of calcium carbonate mixed with 50 mL/kg of soya lecithin. The final product provides an interesting alternative to chemical pesticides for Andean farmers affected by this potato pest

Ape malaria transmission and potential for ape-to-human transfers in Africa

Recent studies have highlighted the large diversity of malaria parasites infecting African great apes (subgenus Laverania) and their strong host specificity. Although the existence of genetic incompatibilities preventing the cross-species transfer may explain host specificity, the existence of vectors with a high preference for a determined host represents another possibility. To test this hypothesis, we undertook a 15-mo-long longitudinal entomological survey in two forest regions of Gabon, where wild apes live, at different heights under the canopy. More than 2,400 anopheline mosquitoes belonging to 18 species were collected. Among them, only three species of Anopheles were found infected with ape Plasmodium: Anopheles vinckei, Anopheles moucheti, and Anopheles marshallii Their role in transmission was confirmed by the detection of the parasites in their salivary glands. Among these species, An. vinckei showed significantly the highest prevalence of infection and was shown to be able to transmit parasites of both chimpanzees and gorillas. Transmission was also shown to be conditioned by seasonal factors and by the heights of capture under the canopy. Moreover, human landing catches of sylvan Anopheles demonstrated the propensity of these three vector species to feed on humans when available. Our results suggest therefore that the strong host specificity observed in the Laveranias is not linked to a specific association between the vertebrate host and the vector species and highlight the potential role of these vectors as bridge between apes and humans

Determination of tsetse challenge and its relationship with trypanosome prevalence in trypanotolerant livestock at sites of the African Trypanotolerant Livestock Network

Reports the determination of tsetse challenge at sites of the African Trypanotolerant Livestock Network and its relationships with trypanosome prevalence for the period 1984-1986. Lists the Network sites with trypanotolerant cattle or sheep together with the tsetse species detected. Discusses tsetse species captured, tsetse relative density, trypanosome infection rates and infection types in tsetse, and tsetse challenge and trypanosome prevalence in trypanotolerant livestock

Ape malaria transmission and potential for ape-to-human transfers in Africa

Recent studies have highlighted the large diversity of malaria parasites infecting African great apes (subgenus Laverania) and their strong host specificity. Although the existence of genetic incompatibilities preventing the cross-species transfer may explain host specificity, the existence of vectors with a high preference for a determined host represents another possibility. To test this hypothesis, we undertook a 15-mo-long longitudinal entomological survey in two forest regions of Gabon, where wild apes live, at different heights under the canopy. More than 2,400 anopheline mosquitoes belonging to 18 species were collected. Among them, only three species of Anopheles were found infected with ape Plasmodium: Anopheles vinckei, Anopheles moucheti, and Anopheles marshallii. Their role in transmission was confirmed by the detection of the parasites in their salivary glands. Among these species, An. vinckei showed significantly the highest prevalence of infection and was shown to be able to transmit parasites of both chimpanzees and gorillas. Transmission was also shown to be conditioned by seasonal factors and by the heights of capture under the canopy. Moreover, human landing catches of sylvan Anopheles demonstrated the propensity of these three vector species to feed on humans when available. Our results suggest therefore that the strong host specificity observed in the Laveranias is not linked to a specific association between the vertebrate host and the vector species and highlight the potential role of these vectors as bridge between apes and humans