Trypanotolerant Cattle Research Articles

Divergent antimicrobial peptide (AMP) and acute phase protein (APP) responses to Trypanosoma congolense infection in trypanotolerant and trypanosusceptible cattle

African animal trypanosomiasis (AAT) is endemic across Sub-Saharan African and is a major constraint to livestock production. The ability of certain cattle breeds to remain productive despite infection is known as trypanotolerance; however, the underlying immune mechanisms contributing to this trait remain poorly understood. Antimicrobial peptides (AMPs) and acute phase proteins (APPs) are evolutionarily conserved effector molecules of the innate immune system that have important roles in the resolution of infection and activation of the adaptive immune response. Expression levels of AMP genes (TAP, LAP, BNBD4, DEFB1, DEFB5 and LEAP2) and APP genes (HP, CP, AGP, LBP, SAA3 and CRP) were investigated using real time quantitative reverse transcription PCR (qRT-PCR) in peripheral blood mononuclear cells (PBMC) isolated from two breeds of African cattle (trypanotolerant N’Dama and trypanosusceptible Boran), experimentally infected with Trypanosoma congolense. Haptoglobin and serum amyloid A (SAA) were also measured in plasma using quantitative protein assays. Results demonstrated that tracheal antimicrobial peptide (TAP) gene expression increased by 32-fold in Boran, compared to only 3-fold in N’Dama, by 14 days post-infection (dpi) and rising to 136-fold at 29dpi in Boran, compared to 47-fold in N’Dama (P<0.05). Protein expression levels of SAA are elevated in N’Dama, rising to 163μg/ml at 14dpi compared with 72μg/ml in Boran. The SAA expression profile mirrors the wave of parasitaemia detected in N’Dama. Seven single nucleotide polymorphisms (SNPs) were identified in the promoter regions of the SAA3 and SAA4 genes, which are predicted to affect transcription factor binding and thereby contributing to the differential patterns of expression detected between the breeds. Whereas elevated TAP expression is a conserved component of the innate immune response to infection in both breeds, higher SAA expression levels may contribute toward trypanotolerance in N’Dama.

Economic assessment of the performance of trypanotolerant cattle breeds in a pastoral production system in Kenya

Cattle are the major source of food security and income for pastoral farmers in sub-Saharan Africa. However, infectious and parasitic diseases remain a major constraint to improved cattle productivity in the region. The use of animal health economics to support decision-making on cost-effective disease control options is increasingly becoming important in the developing world. Trypanotolerant indigenous Orma/zebu cattle in a trypanosomosis-endemic area of Kenya were evaluated for economic performance using gross-margin analysis and partial-farm budgeting. Orma/zebu and Sahiwal/zebu cross-bred cattle were exposed to similar husbandry practices and monitored for growth rate, incidence of common infections (trypanosomosis, anaplasmosis, babesiosis, East Coast Fever and helminthosis) and the cost of treatment assessed. Interview questionnaires were also used to assess the preference rating of the 2 breeds. Results indicated that incidence of infection was trypanosomosis 3%, anaplasmosis 58%, babesiosis 11%, East Coast Fever 22% and helminthosis 28%, with no significant difference between breeds. The Orma/zebu and Sahiwal/zebu breeds had comparable economic benefits, hence a pastoralist in Magadi division is likely to get similar returns from both breeds. This study therefore recommends adoption of not only the Sahiwal/zebu but also the Orma/zebu breed for cattle improvement in trypanosomosis endemic areas and conservation of indigenous genetic resources.

Transcriptional profiling of cattle infected with Trypanosoma congolense highlights gene expression signatures underlying trypanotolerance and trypanosusceptibility.

BackgroundAfrican animal trypanosomiasis (AAT) caused by tsetse fly-transmitted protozoa of the genus Trypanosoma is a major constraint on livestock and agricultural production in Africa and is among the top ten global cattle diseases impacting on the poor. Here we show that a functional genomics approach can be used to identify temporal changes in host peripheral blood mononuclear cell (PBMC) gene expression due to disease progression. We also show that major gene expression differences exist between cattle from trypanotolerant and trypanosusceptible breeds. Using bovine long oligonucleotide microarrays and real time quantitative reverse transcription PCR (qRT-PCR) validation we analysed PBMC gene expression in naïve trypanotolerant and trypanosusceptible cattle experimentally challenged with Trypanosoma congolense across a 34-day infection time course.ResultsTrypanotolerant N'Dama cattle displayed a rapid and distinct transcriptional response to infection, with a ten-fold higher number of genes differentially expressed at day 14 post-infection compared to trypanosusceptible Boran cattle. These analyses identified coordinated temporal gene expression changes for both breeds in response to trypanosome infection. In addition, a panel of genes were identified that showed pronounced differences in gene expression between the two breeds, which may underlie the phenomena of trypanotolerance and trypanosusceptibility. Gene ontology (GO) analysis demonstrate that the products of these genes may contribute to increased mitochondrial mRNA translational efficiency, a more pronounced B cell response, an elevated activation status and a heightened response to stress in trypanotolerant cattle.ConclusionThis study has revealed an extensive and diverse range of cellular processes that are altered temporally in response to trypanosome infection in African cattle. Results indicate that the trypanotolerant N'Dama cattle respond more rapidly and with a greater magnitude to infection compared to the trypanosusceptible Boran cattle. Specifically, a subset of the genes analyzed by real time qRT-PCR, which display significant breed differences, could collectively contribute to the trypanotolerance trait in N'Dama.

Characterisation and validation of farmers’ knowledge and practice of cattle trypanosomosis management in the cotton zone of West Africa

We carried out a knowledge, attitude, practice (KAP) survey on how farmers ( n = 895) manage cattle trypanosomosis in Burkina Faso, Mali and Guinea. Most farmers (96%) recognised the common signs of trypanosomosis, 70% knew the role of tsetse flies in transmitting the disease and 96% had knowledge of drugs used for treatment. Farmers reported that trypanosomosis was the most important cattle disease and estimated that 25% of their herd fall sick each year and 18% of the sick animals die. Nearly all sick animals (90%) were treated with trypanocides and most treatments were administered by untrained farmers. Giving drugs was the strategy most used as primary means of protection (50% of farmers) followed by avoiding high risk areas (32% of farmers) and keeping trypanotolerant cattle (7% of farmers). Few farmers knew about communal tsetse control methods and those who did, rarely practiced them. Farmer diagnosis of trypanosomosis in cattle presented at clinics ( n = 113) was in most cases (84%) supported by laboratory tests. However, the signs that most farmers considered indicative of trypanosomosis (staring coat and emaciation) were poor predictors of trypanosomosis. We tested farmer knowledge of injection sites and trypanocide dilutions ( n = 423 cattle), and while few (15%) farmers gave under-dosages or over-dosage (2% of farmers), injection techniques were poor with injection-related side effects in 24% of cattle treated by farmers. Despite this, therapeutic outcomes were both objectively (clinical parameters) and subjectively (carer assessment) satisfactory in 89% of cattle treated by farmers. This study found that farmers play a major role in successfully managing trypanosomosis and recommends the recognition and support for community based treatment.

Immunology and immunopathology of African trypanosomiasis

Major modifications of immune system have been observed in African trypanosomiasis. These immune reactions do not lead to protection and are also involved in immunopathology disorders. The major surface component (variable surface glycoprotein,VSG) is associated with escape to immune reactions, cytokine network dysfunctions and autoantibody production. Most of our knowledge result from experimental trypanosomiasis. Innate resistance elements have been characterised. In infected mice, VSG preferentially stimulates a Th 1-cell subset. A response of gamma delta and CD8 T cells to trypanosome antigens was observed in trypanotolerant cattle. An increase in CD5 B cells, responsible for most serum IgM and production of autoantibodies has been noted in infected cattle. Macrophages play important roles in trypanosomiasis, in synergy with antibodies (phagocytosis) and by secreting various molecules (radicals, cytokines, prostaglandins,...). Trypanosomes are highly sensitive to TNF-alpha, reactive oxygen and nitrogen intermediates. TNF-alpha is also involved in cachexia. IFN-gamma acts as a parasite growth factor. These various elements contribute to immunosuppression. Trypanosomes have learnt to use immune mechanisms to its own profit. Recent data show the importance of alternative macrophage activation, including arginase induction. L-ornithine produced by host arginase is essential to parasite growth. All these data reflect the deep insight into the immune system realised by trypanosomes and might suggest interference therapeutic approaches.

Physiological genomics special issue on animal functional genomics

this special issue of Physiological Genomics highlights 12 papers that reflect presentations made by 110 international delegates of the 2nd International Symposium on Animal Functional Genomics (2nd ISAFG) held May 16th-19th, 2006, at Michigan State University (East Lansing, MI). This was the second

Efficiency and limits of the Serial Analysis of Gene Expression (SAGE) method: Discussions based on first results in bovine trypanotolerance

Post genomic biotechnologies, such as transcriptome analysis, are now efficient enough to characterize the full complement of genes involved in the expression of specific biological functions. One of them is the Serial Analysis of Gene Expression (SAGE) technique. SAGE involves the construction of transcript libraries for a quantitative analysis of the entire set of genes expressed or inactivated at particular stages of cellular activation. Bioinformatic comparisons in hosts and pathogens genomic databases allow the identification of several up- and down-regulated genes, ESTs and unknown transcripts directly involved in the host–pathogen immunological interaction mechanisms. Based on the first results obtained during an experimental Trypanosoma congolense infection in trypanotolerant cattle, the efficiency and limits of such a technique, from the data acquisition level to the data analysis level, is discussed in this analysis.

Genetic aspects of growth and maturing rate in trypanotolerant beef cattle: N'Dama

Genetic parameters for Absolute Growth Rate (AGR), Relative Growth Rate (RGR) and Absolute Maturing Rate (AMR) at various age interval from birth to maturity in N'Dama beef cattle raised in the humid tropics of Nigeria were estimated. Performance data used were accumulated between 1948 and 1964 at Fasola cattle ranch in Oyo, Nigeria and the number of records analysed ranged from 44 to 678. preweaning (B – W) growth and maturing rates in N'Dama calves were 0.377 + 0.009 kg/day (AGR), 0.643 + 0.006 %/day (RGR) and 0.120 + 0.003% A/day (AMR) and fluctuate subsequently, following the animals' state of development and certain physiological stress conditions. At post weaning (W – 12), these rates decreased to 0.249 + 0.049kg/day, 0.204 + 0.029%/day and 0.075 + 0.014 % A/day for AGR, RGR and AMR respectively. Estimates of heritability at the various age intervals were considered low in these growth traits with values obtained ranging from 0.03 to 0.24 for AGR, 0.03 to 0.21 for RGR and ).02 to 0.42 for AMR, with high standard errors. The low estimates though, consistent with literature reports were attributed to the poor standard of animal management and production environment at Fasola. It was evident from this study that selection of N'Dama calves based on post weaning (W – 12) growth or maturing rates would yield substantial genetic progress. However, improved animal management and production environment on the ranch would not only improve precision of the genetic parameter estimates but would also enhance N'Dama growth performance generally. Keywords: Growth rates, maturing rates, genetic parameters, trypanotolerant cattle.

The Genetics of Trypanotolerance in Cattle: A Review

Trypanosomosis is a major recognized factor limiting livestock productivity. Control of the disease has explored the use of drugs, vector and the farming of trypanotolerant livestock in order to enhance productivity. However, there are documented difficulties with each of the methods. These include drug resistance, re-invasion of controlled areas by tsetse flies and the small population of the trypanotolerant cattle population. Hence the search for genes that will confer trypanosome-resistance and enhance productivity is imperative. Attempts to control trypanosomosis using molecular genetic techniques have continued over the years. In this brief review, the advances made towards an understanding of genetics involved in trypanotolerance will be highlighted. So far, the genome involved in the genetics of trypanotolerance in cattle and in mice, known as the quantitative trait loci (QTL), has been identified using microsattelites. Comparative studies of map data between cattle and mice in the principal QTL region of both species have revealed a region of homology of about 300,000 base pairs (bp) between cattle chromosome 7 and mouse chromosome 17 lying within the principal QTL in both species. This finding points to the possibility that the underlying genes in these two QTL could be the same in cattle and mice and may pave the way for the eventual identification of trypanotolerant genes. The identification of the genes would make it possible to use transgenic approaches that would incorporate resistance to trypanosomosis for control design. Keywords: Genetics, trypanotolerance, cattle Trop. Vet. Vol. 21 (2) 55-60 (2003)

Identification of mechanisms of natural resistance to African trypanosomiasis in cattle

Natural resistance to African trypanosomiasis in certain Bos taurus cattle in West Africa, called trypanotolerance, may hold solutions for control of this economically crippling disease. Comparison of immune responses between trypanotolerant and trypanosusceptible cattle have shown some differences in antibody response, complement level and cytokine expression, but it is not known whether these differences are the cause of resistance. Two experiments were carried out to assess the contribution of the immune and haemopoietic systems to trypanotolerance. The production of haemopoietic chimaeras from trypanotolerant and susceptible twin calves and comparison of their responses after infection with singleton calves, allowed an assessment of the role of the haemopoietic system in trypanotolerance. An in vivo depletion of CD4 cells in the two breeds allowed an appraisal of the role of T and B lymphocytes in trypanotolerance. The results of the two experiments suggest that natural resistance comprises at least two mechanisms, an innate mechanism that controls parasite growth, and another, involving the haemopoietic system, that is able to limit anaemia. This supports the hypothesis that innate mechanisms in trypanotolerant cattle are more efficient in controlling disease, making them less reliant on antibody responses.

The Muturu: A rare sacred breed of cattle in Nigeria

SummaryThe Muturu, a trypanotolerant cattle breed is probably one of the least known breed of cattle in West Africa. Little has been published on its distribution, management, morphological characteristics or biological performance.Early reports showed that the Muturu cattle were once widely distributed across the continent from Liberia, across the West African subregion, to Ethiopia. However, due to expansion of the Zebu population and rapid urbanization, the small bodied animal came under pressure and was found surviving in pockets of the savannahs and in the humid forest zones where it had the comparative advantage of trypanotolerance. The survival of the cattle in the humid and forest zones of Nigeria stems from the fact that the animal is still sacred in so many communities and its milk is widely used for medicinal purposes. In some states of Nigeria, the semi-feral Muturu are not tended but hunted when required for sacrifice.From a population size of 0.4 million heads in 1960, Akinwunmi and Ikpi, (1985) reported a decline in the population of the breed to 50–80 thousand in the late 1980s in Nigeria although RIMS (1992), reported a population growth to 115 172 heads. With limited data bank information on their adaptation and productivity, possible identification of genes that confer resistance to or tolerance of environmental stress in these animals will be of global significance.

Trypanosome infections and tick infestations: susceptibility in N’Dama, Gobra zebu and Gobra×N’Dama crossbred cattle exposed to natural challenge and maintained under high and low surveillance of trypanosome infections

Susceptibility to trypanosome infections and tick infestations was assessed in 51 N’Dama, 48 Gobra zebu and 37 Gobra×N’Dama crossbred (F1) cattle exposed to field-tick infestations and natural high tsetse challenge over more than one year. From these cattle, 12 animals of each breed were randomly selected and examined parasitologically for trypanosome infections and packed cell volume (PCV) twice a week (high surveillance, group HS). In the remaining 100 cattle trypanosome infection and PCV were monitored monthly (low surveillance, group LS). Mortality rates were recorded in both groups. Tick infestation was quantified fortnightly from all animals in group HS and from four to seven randomly selected animals of each breed in group LS. In both HS and LS groups, trypanocidal drug treatment was administered to trypanosome positive animals with PCV equal to or less than 20% or when they showed clinical evidence (dullness, weight loss) of trypanosomosis. In both groups, N’Dama cattle exhibited a superior capacity to control trypanosome infections and limit tick burdens. Particularly, in group HS N’Dama cattle showed lower trypanosome infection rate, higher mean PCV value, lower requirement for trypanocide treatments and lower tick load than crossbred and Gobra cattle in the corresponding group (P<0.05 or greater). This was also true in N’Damas in comparison with crossbreds in group LS. Unfortunately, the high mortality occurring in Gobra cattle in group LS did not allow within group comparative analysis between N’Dama, Gobra and crossbred cattle overall the study period. No death occurred in N’Dama cattle maintained under high surveillance of trypanosome infection, while approximately 8% of crossbreds and 50% of Gobras died of trypanosomosis. In group LS, all Gobra and more than 70% of crossbred cattle died. In this group, mortality in N’Dama was limited to less than 16%. In both groups, differences in mortality were significantly higher (P<0.01) in Gobras than in N’Damas. Within breed, animals of the three breeds maintained under high surveillance of trypanosomal infection showed higher mean PCV values, lower tick burdens and required proportionally less trypanocide treatments than corresponding cattle in group LS. The infection rate in N’Dama under high surveillance was lower in comparison with N’Dama cattle in group LS. There was no significant difference in mortality between groups within the N’Dama breed. Conversely, mortality rates were lower in crossbred and Gobra in group HS than in respective cattle in group LS. It was concluded that cattle of the three breeds suffered from trypanosomosis and that trypanosome infections affected tick susceptibility. However, N’Dama showed a superior ability to limit both the pathological effects of trypanosomosis and the level of tick infestations. Therefore, considering the cost of labour and consumable equipment required for a high surveillance, use of multi-disease resistant N’Dama cattle is recommended for the low-input traditional African farming systems in areas where trypanosomosis, ticks and tick-borne diseases are constraints to livestock production. Additional comparative investigations are needed to assess the impact of high surveillance scheme of trypanosome infection in different production systems in trypanotolerant and trypanosusceptible cattle exposed to different gradients of tsetse challenge.

The effects of work and two planes of nutrition on trypanotolerant draught cattle infected with Trypanosoma congolense

AbstractThirty-two N'Dama bulls aged 3 to 4 years were used to study the interactions between work, trypanosomosis and nutrition. The bulls were randomly allocated to two treatments, working (W) and non-working (N). Half in each treatment were placed on an andropogon hay basal diet (B), the other half on a better quality groundnut hay diet (H). Five days a week, four pairs of animals in the BW group and and four pairs in the HW group pulled weighted sledges four times around a 2056-m track. Loads were set to ensure energy expenditure was equivalent to 1·4 times maintenance. After 4 weeks all 32 bulls were injected intradermally with 104 Trypanosoma congolense organisms. The trial continued for a further 8 weeks.Trypanosome infection caused a significant (P &lt; 0·001) decline in packed cell volume (PCV), and the anaemia was more severe (P &lt; 0·05) in working animals; three pairs in the HW group and two pairs in the BW group were withdrawn because PCV fell below 17%. Diet had no effect on PCV or parasitaemia. Infection caused a decline in food intake (P &lt; 0·001) but with significant interactions between diet and work. Intake patterns were similar in the BN and BW groups whilst the HW animals consumed significantly more groundnut hay compared with the HN group (P &lt; 0·01). However, nutrition had no significant effect on lap times or the team's ability to work under trypanosomosis challenge. Post-infection, diet was the dominant factor determining weight change, HN and HW animals weighed significantly more than BN and BW animals (P &lt; 0·01) and the interaction between period, diet and work demonstrated that BWhad the lowest weights in the latter stages of the trial (P &lt; 0·05).The results suggest that supplementation with better quality forages confers no benefit to an animal infected with trypanosomes. Nor can trypanotolerant cattle sustain long periods of work if subiected to a primary challenge of trypanosomes.

Studies on host resistance to tick infestations among trypanotolerant Bos indicus cattle breeds in east Africa.

Recent epidemiological studies carried out in East Africa have indicated that some Bos indicus cattle breeds such as the Orma Boran and Maasai Zebu have a degree of trypanotolerance worth exploitation by their introduction into trypanosomosis endemic areas where other cattle breeds cannot survive. However, in most areas of East Africa, trypanosomosis, ticks, and tick-borne diseases occur together. It is therefore important to obtain information on the susceptibility of these breeds to tick infestation and tick-borne diseases. This study was therefore designed to determine the susceptibility of these cattle breeds to tick infestations. They were compared with the Galana Boran (trypanosusceptible) and the Friesian (susceptible to tick infestations, tick-borne diseases, and trypanosomosis). The four breeds of cattle were exposed to natural tick challenge for a period of seven months and whole body weekly tick counts were done on each animal. Significant differences to tick infestations among the four breeds were observed. For both Rhipicephalus appendiculatus and Boophilus decoloratus, susceptibility to infestation increased in the order, Maasai Zebu, Orma Boran, Galana Boran and Friesian. The results generated by this pilot study so far suggest that variation in susceptibility to tick infestations exists among the four breeds. The Orma Boran and Maasai Zebu showed greater resistance to tick-infestations than the Galana Boran and Friesian. This suggests that utilization of these trypanotolerant cattle breeds could be feasible even in the face of tick challenge and should therefore be considered when planning integrated trypanosomosis and tick control strategies.

Susceptibility of the Namchi and Kapsiki cattle of Cameroon to trypanosome infection.

Two indigenous Cameroonian taurine cattle breeds (Namchi and Kapsiki) were evaluated for trypanosusceptibility following inoculation with Trypanosoma congolense. The degree of zebu ancestry in the experimental animals was assessed using 6 microsatellite markers which are known to have certain unique alleles which are diagnostic of Bos indicus genetic input. Their response to the infection was compared to that of known trypanotolerant (N'Dama) and trypanosusceptible (Ngaoundere Gudali) cattle. The Namchi and the N'Dama controlled the development and severity of anaemia and parasitaemia better than the Kapsiki and the Gudali. For these parameters, there was no significant difference between the N'Dama and Namachi nor between the Kapsiki and Gudali. Similarly, weight loss showed significant breed variation. The N'Dama lost the least weight and the Kapsiki the most. Zebu introgression in the Namchi was comparable to that in the N'Dama while that of the Kapsiki breed was higher, indicating a high level of cross breeding. From the results, the Namchi are considered trypanotolerant while the Kapsiki are trypanosusceptible. The potential exploitation of the indigenous Namchi cattle is discussed.

The influence of plane of nutrition on the effects of infection with Trypanosoma congolense in trypanotolerant cattle

Thirty-two N'Dama heifers were offered ad libitum Andropogon hay plus 10·2 g/kg liveweight (LW) groundnut hay (GNH) (L) or 10·2 g/kg LW GNH and 3·9 g/kg LW groundnut cake (GNC) (H). After 4 weeks on the diets, half of each group were infected intradermally with Trypanosoma congolense clone (ITC 50) (LI and HI). Peak parasitaemia occurred 6–8 days after infection and started to decrease c. 56 days later. No differences in parasitaemia were observed between LI and HI animals. Packed cell volume (PCV) fell in all treatments (by 5·4, 13·8, 3·7 and 9·4 units after 49–63 days post-infection (p.i.) for the L, LI, H and HI groups respectively) and significant effects of infection and diet were observed. GNH and GNC intakes were maintained during the trial; however, infected animals had a decreased intake of Andropogon hay. LI animals lost significantly more weight during the experimental period than the non-infected controls (−71·4 v. −13·7 g/day). Meanwhile, HI animals gained less weight compared with the H group (52·2 v. 167·6 g/day). Weight losses appeared to be due to decreased food intake. In the period 54–68 days p.i., plasma concentrations of albumin were lower and plasma protein was higher in infected animals. Plasma cholesterol concentrations were also lower in infected animals 54–68 days p.i. Plasma urea concentrations were higher in supplemented animals but were not affected by infection. The results showed that animals on a higher plane of nutrition showed less severe clinical signs of infection. However, for all the parameters considered, the magnitude of the difference between groups on different diets was similar for both infected and control animals, suggesting that mechanisms of resistance were not affected by the planes of nutrition considered.

Trypanosoma congolense:A Comparison of T-Cell-Mediated Responses in Lymph Nodes of Trypanotolerant and Trypanosusceptible Cattle during Primary Infection

A comparison of T-cell-mediated immune responses in trypanotolerant N'Dama and susceptible Boran cattle during primary infection with tsetse-transmittedTrypanosoma congolensewas conducted to assess whether different patterns of T-cell activation occurred during trypanosome infection. Proliferation and IFN-γ synthesis in response to trypanosome antigens and to the mitogen Con A were measured in LNC before infection and 10 and 35 days postinfection. Phenotypic analysis of LNC was also carried out. No significant differences in thein vitroproliferation of LNC to VSG, to hsp70/BiP, or to Con A were detected between the breeds. In contrast, IFN-γ production in response to Con A was higher in Boran cattle at 35 days p.i. A reduction in the number of CD2+ and CD4+ T-cells and an increase in the percentage of B-cells, CD8+ T-cells, and γδ T-cells during infection in both N'Dama and Boran was revealed by cytofluorimetric analysis of lymph node cells.

The effect of trypanosomosis on pregnancy in trypanotolerant Orma Boran cattle

A study was undertaken to investigate the influence of trypanosomosis on the outcome of pregnancy in trypanotolerant Orma Boran (Bos indicus) exposed to natural tsetse challenge in an area of Kenya infested predominantly with Glossina pallidipes . Of 73 pregnant Orma heifers, 58 (79.5%) produced live calves at term, 13 (17.8%) aborted and 2 (2.7%) died of trypanosomosis. Of the 71 surviving animals, 22 (31%) were infected with Trypanosoma vivax . 21 (29.6%) T. congolense . and 26 (36.6%) had mixed infections with T. vivax and T. congolense . These results suggest that in areas of high trypanosomosis risk reproductive function is affected even in trypanotolerant cattle, and that both T. vivax and T. congolense can be responsible for the abortions observed in the field. It is suggested that maintenance of pregnancy in the face of trypanosome challenge was dependent on individual variation among the Orma cattle, but as challenge increased beyond the limits of effectiveness of trypanotolerance, disruption of pregnancy occurred.

Trypanosoma congolense:B-Lymphocyte Responses Differ between Trypanotolerant and Trypanosusceptible Cattle

Trypanosomiasis is a serious constraint to livestock production in sub-Saharan Africa. Some breeds of cattle are genetically more resistant to the pathogenic effects of trypanosome infection. We measured B-cell activation and the quantity and isotype of antibody produced at the cellular level in six trypanotolerant N'Dama and five trypanosusceptible Boran cattle. The frequencies of spleen cells secreting total and parasite-specific IgM and IgG were measured prior to and 16, 28, and 35 days after a primary challenge withTrypanosoma congolense.Boran cattle had higher frequencies of splenic cells secreting IgM specific for trypanosome-derived variable surface glycoprotein (VSG), cysteine protease (congopain, CP), and heat shock protein (hsp70/BiP) and the nonparasite antigen, ovalbumin, than did N'Dama cattle. In contrast, the number of VSG-specific IgG-secreting cells was significantly greater in N'Dama than in Boran cattle. During infection, low titers of anti-VSG IgM were detected transiently in the serum of all animals. However, N'Dama had significantly more VSG-specific IgG in blood than Boran during infection. The peripheral blood mononuclear cell population of N'Dama cattle contained a higher percentage of surface IgM-positive B-cells prior to and throughout infection than were found in the blood of Boran. In addition, during infection N'Dama cattle had more circulating lymphocytes that could be activatedin vitroto undergo differentiation into IgM- and IgG-secreting cells. These findings demonstrate differences in the frequency of trypanosome-specific antibody-secreting cells in the spleen and in the activation state of B-cells in the blood between N'Dama and Boran cattle during a primary infection withT. congolense.

Profitability, efficiency and comparative advantage of African cattle meat and milk production: the case of trypanotolerant village cattle production

AbstractTrypanosomiasis is a major constraint to increased food production in Africa as it limits livestock production and mixed farming over an area of 10 million km2. The use of African trypanotolerant breeds of cattle is one approach to control trypanosomiasis that is being given increasing attention. This paper examines under what circumstances trypanotolerant village cattle enterprises can be economically viable in regions of origin and areas of introduction. On‐going production is analysed in four countries using cost‐benefit analyses. Comparative advantage and subsidies received are also estimated. Results indicate that resources for trypanotolerant cattle production are efficiently allocated as the sector has a comparative advantage and contributes effectively to the national welfare. Financial returns to producers are attractive and by comparing social and private prices important constraints are identified to improve profitability.