Prevalence Of Trypanosome Infections Research Articles

Response of Nkedi Zebu and Ankole cattle to tick infestation and natural tick-borne, helminth and trypanosome infections in Uganda

A cross-sectional study was conducted in Soroti district of Uganda to establish important traits of Nkedi Zebu and Ankole cattle regarding their production performance responses to natural infections of trypanosomes, gastrointestinal nematodes, Theileria parva, Babesia bigemina, Anaplasma marginale and tick infestations. Over four visits between October 2006 to August 2007, tick counts were performed and blood, faecal samples and sera were collected from the Nkedi Zebu (295) and Ankole (165) cattle from 86 herds in six locations per visit. Low parasitological prevalence of trypanosome infection (<6%) and high prevalence of gastrointestinal nematode infections (>30%) with low faecal egg counts (110-300 eggs per gramme (EPG)) were observed in the Nkedi Zebu and Ankole cattle. Both breeds had high, moderate and low mean counts of Rhipicephalus appendiculatus (18.0-24.0), Rhipecephalus (Boophilus) decoloratus (3.6-10.3) and Amblyomma variegatum ticks (1.7-4.3), respectively. In addition, both breeds had similar mean packed cell volumes (26.4-31.2) and a similar percentage of animals were anaemic (14.5-36.6%). The Nkedi Zebu cattle further had higher mean optical density (OD) values for antibodies against T. parva (1.093-1.445) and A. marginale infections (0.573-0.583), and significantly (P < 0.001) higher mean OD values of antibodies against B. bigemina infections (1.07-2.175) than the Ankole cattle: T. parva (1.030-1.302); A. marginale (0.442-0.603) and B. bigemina infections (0.863-2.154). The Ankole cows produced significantly more (P < 0.001) milk per day (2.68L) than the Nkedi Zebu cows (1.98L), and the Ankole oxen had significantly higher (P < 0.05) draught power output (2.57days/acre) than the Nkedi Zebu oxen (2.93days/acre). Liveweights of calves aged 0-12months of both breeds were comparable, suggesting that the Nkedi Zebu and Ankole cattle under similar disease challenge exhibited similar growth rates. In conclusion, the Nkedi Zebu cattle seem to possess a higher degree of disease resistance against endemic parasitic diseases, while the Ankole cattle seem to possess a moderate degree of disease resistance coupled with a moderate production potential.

Prevalence of trypanosome infections in dogs from Chagas disease endemic regions in Panama, Central America

The prevalence of canine trypanosomosis was investigated in two Chagas disease endemic rural communities located in the central region of Panama. Serologic tests for Trypanosoma cruzi infection revealed a prevalence of 11.1%. Hemocultures coupled with PCR analysis demonstrated a Trypanosoma rangeli infection rate of 5.1%. An overall trypanosome infection index of 16.2% (16/99) was detected in this canine population. One dog had a mixed infection of T. cruzi and T. rangeli. Six of the trypanosome-infected dogs belong to people who were diagnosed of Chagas disease. We conclude that dogs from this rural area of Panama are frequently infected with trypanosomes transmitted by the sylvatic vector, Rhodnius pallescens, and suggest that dogs are important in the peridomestic transmission cycle of trypanosomes as reservoirs and hosts. The epidemiological implications of these findings are discussed.

Bovine trypanosomosis and its vectors in two districts of Bench Maji zone, South Western Ethiopia

A cross-sectional study was carried out from November 2008 to February 2009 in Guraferda and Sheko districts of Bench Maji Zone, South Western Ethiopia. The objective of the study was to determine the prevalence of bovine trypanosomosis and the density of its vectors. An overall prevalence of trypanosome infection in the study area was 4.4%. Trypanosoma congolense (36.36%) was the dominant trypanosome species followed by Trypanosoma vivax (18.18%) and Trypanosoma brucei (9.09%). Mean packed cell volume value of parasitemic animals (21.8%) was significantly (P<0.05) lower than that of aparasitemic animals (27.7%). Biconical and NGU traps were deployed for 72 h, and the result indicated Glossina pallidipes followed by Glossina fuscipes as the only tsetse fly species caught in the study area along with other biting flies like Stomoxys and Tabanus. The apparent density of tsetse flies was 2.83 flies trap(-1) day(-1). NGU trap caught more of G. pallidipes while biconical trap caught more G. fuscipes, and the difference was significant (P<0.05). Although the current study indicated low prevalence of trypanosomosis in the study area, the impacts of trypanosomosis on cattle production and productivity should not be neglected. Therefore, attention should be given to control the disease and also the vector.

High trypanosome infections in &lt;i&gt;Glossina palpalis palpalis&lt;/i&gt; Robineau-Desvoidy 1830 in southern Kaduna state, Nigeria

A survey was undertaken to determine the prevalence of trypanosome infection in Glossina species in Kaura Local Government Area (LGA) of Kaduna State, Southern Guinea Savanna, Nigeria, aimed at identifying areas to be prioritized for area-wide tsetse eradication. The flies were trapped from a relic forest and also from 22 locations spread within the LGA and dissected to determine infection rates and infection types. Glossina palpalis palpalis Robineau-Desvoidy 1830 was the only tsetse species encountered both within the relic forest and the 22 locations sampled; its distribution was strictly riverine. Out of the 409 non-teneral flies dissected in the relic forest, 18.1 ± 0.02%, were infected with trypanosomes, with infections of the vivax -group dominating (76.92%) over the congolense group (23.01%). Of the 690 flies caught from 22 locations, 9.9 ± 1.0% were infected, 69.12% with vivax -group and 30.88% with congolense -group. Infections of the brucei -group were not encountered throughout the investigation period. The high prevalent figure of 12.64% recorded in the flies from both the relic forest and other locations portray the area as highly risky, with Bondong, Manchok and Kadarko districts being highly endemic, followed by a region of medium prevalence at Kukum district and a region of low endemicity within the mountain ranges of Zankan district. A well articulated vector eradication programme that will target G. p. palpalis and the various species of other biting dipterans is recommended as the solution to the recurring nagana problem in the area.

Constraints to estimating the prevalence of trypanosome infections in East African zebu cattle

BackgroundIn East Africa, animal trypanosomiasis is caused by many tsetse transmitted protozoan parasites including Trypanosoma vivax, T. congolense and subspecies of T. brucei s.l. (T. b. brucei and zoonotic human infective T. b. rhodesiense) that may co-circulate in domestic and wild animals. Accurate species-specific prevalence measurements of these parasites in animal populations are complicated by mixed infections of trypanosomes within individual hosts, low parasite densities and difficulties in conducting field studies. Many Polymerase Chain Reaction (PCR) based diagnostic tools are available to characterise and quantify infection in animals. These are important for assessing the contribution of infections in animal reservoirs and the risk posed to humans from zoonotic trypanosome species. New matrices for DNA capture have simplified large scale field PCR analyses but few studies have examined the impact of these techniques on prevalence estimations.ResultsThe Whatman FTA matrix has been evaluated using a random sample of 35 village zebu cattle from a population naturally exposed to trypanosome infection. Using a generic trypanosome-specific PCR, prevalence was systematically evaluated. Multiple PCR samples taken from single FTA cards demonstrated that a single punch from an FTA card is not sufficient to confirm the infectivity status of an individual animal as parasite DNA is unevenly distributed across the card. At low parasite densities in the host, this stochastic sampling effect results in underestimation of prevalence based on single punch PCR testing. Repeated testing increased the estimated prevalence of all Trypanosoma spp. from 9.7% to 86%. Using repeat testing, a very high prevalence of pathogenic trypanosomes was detected in these local village cattle: T. brucei (34.3%), T. congolense (42.9%) and T. vivax (22.9%).ConclusionsThese results show that, despite the convenience of Whatman FTA cards and specific PCR based detection tools, the chronically low parasitaemias in indigenous African zebu cattle make it difficult to establish true prevalence. Although this study specifically applies to FTA cards, a similar effect would be experienced with other approaches using blood samples containing low parasite densities. For example, using blood film microscopy or PCR detection from liquid samples where the probability of detecting a parasite or DNA molecule, in the required number of fields of view or PCR reaction, is less than one.

Prevalence of trypanosome infections in ruminants in the Southern Guinea Savanna, Nigeria.

A survey was conducted to determine the prevalence of trypanosomes in cattle and sheep in Kaura Local Government Area (LGA) of Kaduna State, southern guinea savanna, Nigeria. Animals were sampled in 12 villages from the districts of Bondong, Fada, Kadarko, Kukum, Manchok and Zankan. Sampling visits were undertaken on seasonal basis in the late wet season (October), early dry season (December), late dry season (February) and early wet season (June). Three- ml blood samples were collected from the jugular vein of 395 cattle and 37 sheep. The results revealed that 21.53 ± 1.97% (range 9.4-43.8% per village) of the total animals were infected with various species of trypanosomes, with the prevalence in bovine and ovine being 20.51 ± 2.03% and 32.43 ± 7.69% respectively. Trypanosoma vivax had the highest infection rates (64.52%), followed by T. brucei (18.30%) and T. congolense (17.20%). Infections varied significantly among the districts, ranging from 9.7% at Zankan to 36.9% at Manchok (t=13.08; df=3; p

Tripartite interactions between tsetse flies, Sodalis glossinidius and trypanosomes—An epidemiological approach in two historical human African trypanosomiasis foci in Cameroon

Epidemiological surveys were conducted in two historical human African trypanosomiasis foci in South Cameroon, Bipindi and Campo. In each focus, three sampling areas were defined. In Bipindi, only Glossina palpalis was identified, whereas four species were identified in Campo, G. palpalis being highly predominant (93%). For further analyses, 75 flies were randomly chosen among the flies trapped in each of the six villages. Large and statistically significant differences were recorded between both (1) the prevalence of Sodalis glossinidius (tsetse symbiont) and the prevalence of trypanosome infection of the major fly species G. p. palpalis and (2) the respective prevalence of symbiont and infection between the two foci. Despite these differences, the rate of infected flies harbouring the symbiont was very similar (75%) in both foci, suggesting that symbionts favour fly infection by trypanosomes. This hypothesis was statistically tested and assessed, showing that S. glossinidius is potentially an efficient target for controlling tsetse fly vectorial competence and consequently sleeping sickness.

Prevalence of trypanosomes from Clarius batrachus (Linnaeus) of Purba Medinipur, West Bengal, India

AbstractHaemoflagellates of the genus Trypanosoma Gruby, 1843 are prevalent in fresh water fishes and are transmitted by leech. A total of 133 Clairus batrachus were examined for haemoflagelates. The fishes were collected from ponds and water bodies of Purba Medinipur district, West Bengal, India, from January, 2006 to July, 2007. The slides were prepared taking blood from both males (97) and females (36). It was found that only 19 out of 36 (52.78%) females and 31 out of 97 (31.95%) males were infected. Thus females were recorded with a higher prevalence of trypanosome infection than males. There was a significant difference (P&lt;0.05) in the infection rate with trypanosomes in males and females.

The Prevalence Of Trypanosome Infection In Trade Cattle, Goats And Sheep Slaughtered At The Kaduna Abattoir

The prevalence of trypanosome infection in trade cattle, goats and sheep was investigated in slaughtered animals at the Kaduna Abattoir. Wet, thin, thick films, animal inoculation, haematocrit centrifugation technique and buffy coat methods were used to detect rypanosomes in the jugular blood of the animals. The packed cell volume (PCV) was also determined. A total of 300 cattle, 300 goats and 300 sheep were examined within five months (September, 1998 – January, 1999) and the prevalence rates in cattle, goats and sheep were found to be 5.00%, 4.67% and 3.33% respectively. Mean PCV of infected cattle was 20.33% against uninfected cattle 35.08%. In goats, the PCV was 20.29%, uninfected goats 31.56%; while that of sheep was 19.40% and uninfected 32.85%. Trypanosoma vivax infection accounted for 60%, T. brucei 26.67% and T. congolense 13.33% in cattle. In goats, T. vivax infection accounted for 71.43%, T. brucei 21.43% and T. congolense 7.14%. Also T. vivax infection accounted for 70%, T. brucei 30% and T. congolense 0% in sheep. Sex did not significantly (P>0.05) affect infection rates. Although the prevalence rate of trypanosomiasis in cattle, goats and sheep appeared low compared with the previous works, natural trypanosomiasis remains economically importance in cattle, goats and sheep in Nigeria.African Journal of Clinical and Experimental Microbiology Vol. 10 (1) 2009: pp. 15-25

Evolutionary history of trypanosomes from South American caiman (Caiman yacare) and African crocodiles inferred by phylogenetic analyses using SSU rDNA and gGAPDH genes

In this study, using a combined data set of SSU rDNA and gGAPDH gene sequences, we provide phylogenetic evidence that supports clustering of crocodilian trypanosomes from the Brazilian Caiman yacare (Alligatoridae) and Trypanosoma grayi, a species that circulates between African crocodiles (Crocodilydae) and tsetse flies. In a survey of trypanosomes in Caiman yacare from the Brazilian Pantanal, the prevalence of trypanosome infection was 35% as determined by microhaematocrit and haemoculture, and 9 cultures were obtained. The morphology of trypomastigotes from caiman blood and tissue imprints was compared with those described for other crocodilian trypanosomes. Differences in morphology and growth behaviour of caiman trypanosomes were corroborated by molecular polymorphism that revealed 2 genotypes. Eight isolates were ascribed to genotype Cay01 and 1 to genotype Cay02. Phylogenetic inferences based on concatenated SSU rDNA and gGAPDH sequences showed that caiman isolates are closely related to T. grayi, constituting a well-supported monophyletic assemblage (clade T. grayi). Divergence time estimates based on clade composition, and biogeographical and geological events were used to discuss the relationships between the evolutionary histories of crocodilian trypanosomes and their hosts.

Detection ofTrypanosoma bruceiin Field-Captured Tsetse Flies and Identification of Host Species Fed on by the Infected Flies

The prevalence of trypanosome infections in tsetse flies in the Chiawa area of Lower Zambezi in Zambia, with endemic trypanosomosis, was determined by a polymerase chain reaction (PCR) method that allowed the detection of trypanosome DNA and determination of the type of animal host fed on by the tsetse fly Glossina pallidipes, using tsetse-derived DNA extracts as templates. Ninety G. pallidipes (82 females and 8 males; 18.3%) of the 492 flies captured by baited biconical traps tested positive for the presence of Trypanosoma brucei species genomic DNA. Of the 90 T. brucei-positive flies, 47 (52.2%) also tested positive for vertebrate mitochondrial DNA. Sequence analysis of the vertebrate mitochondrial DNA amplicons established that they originated from 8 different vertebrate species, namely, human (Homo sapiens), African elephant (Loxodonta cyclotis), African buffalo (Syncerus caffer), waterbuck (Kobus ellipsiprymnus), roan antelope (Hippotragus equinus), greater kudu (Tragelaphus strepsiceros), warthog (Phacochoerus africanus), and goat (Capra hircus). Furthermore, to investigate the prevalence of trypanosome infections in domestic goats in the same area where trypanosomes had been detected in tsetse files, a total of 86 goats were randomly selected from 6 different herds. Among the selected goats, 36 (41.9%) were found to be positive for T. brucei species. This combined detection method would be an ideal approach not only for mass screening for infection prevalence in tsetse populations, but also for the prediction of natural reservoirs in areas endemic for trypanosomosis.

Virological and Serological Studies of Porcine Respiratory Coronavirus Infection on a Japanese Farm

The prevalence of trypanosome infections in tsetse flies, Glossina pallidipes, collected from Chiawa and Chakwenga in Zambia with endemic trypanosomosis was assessed by polymerase chain reaction (PCR). Out of the 550 G. pallidipes, 58 (10.5%) flies were found to harbor trypanosome DNA. Infection rates of tsetse with Trypanosoma vivax universal, Trypanosoma congolense savannah, T. congolense forest and T. congolense kilifi were 4.2% (23/550), 4.7% (26/550), 1.1% (6/550) and 1.6% (9/550), respectively. To determine the mammalian hosts of T. congolense and T. vivax infections from the tsetse flies, mammalian mitochondrion DNA of blood meal in these flies were analyzed by PCR and subsequent gene sequence analysis of the amplicons. Sequence analysis showed the presence of cytochrome b gene (cyt b) of 7 different mammalian species such as human, elephant, buffalo, goat, warthog, greater kudu and cattle. Goats which were main livestock in these areas were further examined to know the extent of its contribution in spreading the infection. We examined the prevalence of trypanosome infections in the domestic goat population in 6 settlements in Chiawa alone. Of the 86 goats sampled, 4 (4.6%), 5 (5.8%), 4 (4.6%) and 4 (4.6%) were positive for T. vivax universal, T. congolense savannah, forest and kilifi, respectively. These findings showed that the host-source of trypanosome infections in vector fly give a vital information about spread of infection. The result of this study will certainly contribute in elucidating more the epidemiology of trypanosomosis.

The comparative role of cattle, goats and pigs in the epidemiology of livestock trypanosomiasis on the plateau of eastern Zambia

To determine and compare the prevalence of trypanosome infections in different livestock species (cattle, pigs and goats) in areas where game animals are scarce and livestock constitute the main food source of tsetse, a survey was conducted on the plateau of the Eastern Province of Zambia in Katete and Petauke districts where Glossina morsitans morsitans is the only tsetse species present. Blood was collected from a total of 734 cattle, 333 goats and 324 pigs originating from 59 villages in both districts and was examined using the buffy coat method and the PCR-RFLP as diagnostic tools.The prevalence of trypanosome infections differed substantially between livestock species. Using microscopic diagnostic methods, trypanosome infections were detected in 13.5% of the cattle and 0.9% of the pigs. All goats were parasitologically negative. The PCR-RFLP analyses increased the trypanosomiasis prevalence to 33.5, 6.5 and 3.3% in cattle, pigs and goats respectively. The majority of the infections (91.2%) were due to Trypanosoma congolense. The presence of a trypanosome infection in cattle and pigs resulted in a significant decline in the packed cell volume. The outcome of the study clearly shows that despite the availability of goats and pigs, cattle seem to be the major livestock species affected by the disease in trypanosomiasis endemic areas. The high proportion of infections in cattle could be partly attributed to their higher availability and attractiveness to tsetse.

Innate immune responses regulate trypanosome parasite infection of the tsetse fly Glossina morsitans morsitans

Tsetse flies transmit the protozoan parasite African trypanosomes, the agents of human sleeping sickness in sub-Saharan Africa. Parasite transmission in the insect is restricted by a natural resistance phenomenon (refractoriness). Understanding the mechanism of parasite resistance is important as strengthening fly's response(s) via transgenic approaches can prevent parasite transmission and lead to the development of novel vector control strategies. Here, we investigated the role of one of the two major pathways regulating innate immunity in invertebrates, the immunodeficiency (Imd) pathway, for Glossina morsitans morsitans's natural defence against Trypanosoma brucei spp. infections. We determined the molecular structure of the Imd pathway transcriptional activator Relish (GmmRel), which shows high amino acid identity and structural similarity to its Drosophila homologue. Through a double-stranded RNA-based interference approach, we showed that the pathogen-induced expression profile of the antimicrobial peptides (AMPs) attacin and cecropin is under the regulation of GmmRel. Unexpectedly, the AMP diptericin appears to be constitutively expressed in tsetse independent of the presence of the Rel factor. Through GmmRel knock-down, we could successfully block the induction of attacin and cecropin expression in the immune responsive tissues fat body and proventriculus (cardia) following microbial challenge. The midgut and salivary gland trypanosome infection prevalence, as well as the intensity of midgut parasite infections were found to be significantly higher in flies when attacin and relish expression were knocked down. Our results provide the first direct evidence for the involvement of antimicrobial peptides in trypanosome transmission in tsetse.

Epidémiologie de la trypanosomose bovine dans la région du bassin de l’Abay (Nil bleu), nord-ouest de l’Ethiopie

L’étude a été menée entre Septembre 2003 et Avril 2004 dans les districts de Denbecha et de Jabitehanan situés à basse (&lt; 1 600 m) et moyenne altitudes (1 600–2 000 m). Les objectifs de cette étude ont été de générer des données épidémiologiques sur les tsé-tsé et la trypanosomose, et sur la connaissance de cette maladie par les communautés locales. Les résultats d’un questionnaire ont montré que la trypanosomose était le problème majeur affectant les animaux et entravant les activités agricoles de la zone. Le suivi entomologique a révélé la présence de Glossina morsitans submorsitans, seule espèce de glossine de la zone, ainsi que de tabanidés et de muscidés. Les densités apparentes (mouches/piège/jour) ont été significativement plus élevées (p &lt; 0,05) à la fin de la saison des pluies (1,08, 8,78 et 91 respectivement pour G. m. submorsitans, les tabanidés et les muscidés) qu’en saison sèche (respectivement 0,68, 0,35 et 7,33). Dans les zones de basse altitude, la densité apparente de G. m. submorsitans a été significativement plus élevée (p &lt; 0,05) que dans les zones de moyenne altitude à chaque saison. Un total de 1 648 animaux ont été examinés pour la trypanosomose par la méthode de centrifugation en tube microhématocrite ; les prévalences saisonnières ont été significativement différentes (p &lt; 0,05) avec 17,07 p. 100 en fin de saison des pluies et 12,35 p. 100 en saison sèche. Les taux d’infection ont été plus élevés (p &lt; 0,05) dans les zones de basse altitude (19,87 et 17,62 p. 100 respectivement à la fin de la saison des pluies et en saison sèche) que dans les zones de moyenne altitude (13,39 et 6,54 p. 100). Les valeurs moyennes de l’hématocrite des animaux infectés et apparemment non infectés ont été respectivement de 20,7 ± 3,5 et 26,6 ± 4,3 (p &lt; 0,001) en fin de saison des pluies et de 21,4 ± 3,6 et 26,6 ± 4,3 (p &lt; 0,001) en saison sèche. L’analyse de régression a montré qu’à chaque saison l’hématocrite moyen du troupeau diminuait quand la prévalence de la trypanosomose augmentait.

Prevalence of trypanosome infections in marine fishes from western Norway

Marine fishes from several locations along the west coast of Norway were examined for trypanosome infections. In total, 1640 fishes representing 63 species and 33 families were examined for trypanosome infections. Of these, 19 species of teleosts from eight families were found to be infected, mostly benthic codfish and flatfish in addition to Chelidonichthys gurnardus (L.) and Lophius piscatorius L. Trypanosomes in all fish species appeared to belong to a single form, considered identical to a trypanosome transmitted by the leech Calliobdella nodulifera (Malm, 1863). In the fjords near Bergen, west Norway, trypanosome infections appeared to be restricted to fishes caught deeper than 50 m, probably reflecting a limited bathymetric distribution of the leech vector. Available evidence suggests that the trypanosome parasitaemias decline and become undetectable in a year or less. Despite this, prevalence appeared unaffected by fish size in some species and increased with length in some slow growing species. Th...

Differences in susceptibility to trypanosome infection between Nkedi Zebu and Ankole cattle, under field conditions in Uganda

A cross-sectional study was conducted in tsetse-infested areas of Soroti district in Uganda, with the aim of assessing the response of the Nkedi Zebu and Ankole breeds of cattle to trypanosome infection. Overall, 1215 Nkedi Zebu and 260 Ankole cattle kept under similar levels of tsetse challenge were examined for trypanosome infection, using the Buffy-coat technique and haematocrit centrifugation, and had their packed-cell volumes (PCV) measured. As expected, the infected cattle, whether of the Nkedi Zebu (26.7% v. 29.6%; P < 0.05) or Ankole breeds (24.9% v. 29.1%; P < 0.05), had significantly lower mean PCV than the uninfected. In the Nkedi Zebu cattle, the prevalence of trypanosome infection was lower (7.9% v. 10.8%; P > 0.05) and the overall mean PCV was significantly higher (29.4% v. 28.7%; P < 0.05) than in the Ankole. Compared with the Ankole, Nkedi Zebu cattle appear to be less susceptible to (detectable) trypanosome infection and to the trypanosome-attributable lowering of their PCV.

An antimicrobial peptide with trypanocidal activity characterized from Glossina morsitans morsitans

Tsetse flies (Diptera:Glossinidae) are vectors of African trypanosomes, the protozoan agents of devastating diseases in humans and animals. Prior studies in trypanosome infected Glossina morsitans morsitans have shown induced expression and synthesis of several antimicrobial peptides in fat body tissue. Here, we have expressed one of these peptides, Attacin (GmAttA1) in Drosophila (S2) cells in vitro. We show that the purified recombinant protein (recGmAttA1) has strong antimicrobial activity against Escherichia coli-K12, but not against the enteric gram-negative symbiont of tsetse, Sodalis glossinidius. The recGmAttA1 also demonstrated inhibitory effects against both the mammalian bloodstream form and the insect stage Trypanosoma brucei in vitro (minimal inhibitory concentration MIC 50 0.075 μM). When blood meals were supplemented with purified recGmAttA1 during the course of parasite infection, the prevalence of trypanosome infections in tsetse midgut was significantly reduced. Feeding fertile females GmAttA1 did not affect the fecundity or the longevity of mothers, nor did it affect the hatchability of their offspring. We discuss a paratransgenic strategy, which involves the expression of trypanocidal molecules such as recGmAttA1 in the midgut symbiont Sodalis in vivo to reduce trypanosome transmission.

Seasonal prevalence of bovine trypanosomosis in a tsetse-infested zone and a tsetse-free zone of the Amhara Region, north-west Ethiopia

During a period of four consecutive years, trypanosomosis surveys were conducted in a tsetse-infested and tsetse-free area of the Amhara Region of north-west Ethiopia. In each study area randomly selected communal cattle were sampled and their blood was investigated using parasitological diagnostic methods. At the same time the population of biting flies was sampled. The monthly average prevalence of trypanosome infections in cattle did not differ significantly between study areas. In both study areas, the prevalence of trypanosome infections was highest during the long rainy season. Trypanosome infections were mainly due to Trypanosoma vivax and they significantly reduced the average packed cell volume and the body condition of the animals. The monthly prevalence of infection was correlated with the density of biting flies, such as Tabanidae and Stomoxys spp., in the preceding month suggesting an important role of mechanical transmission in the epidemiology of trypanosomosis in both areas.

Field studies of drug-resistant cattle trypanosomes in Kénédougou Province, Burkina Faso

Field studies were conducted to assess the occurrence of resistance to isometamidium chloride and diminazene aceturate in trypanosomes infecting cattle in Kénédougou Province of Burkina Faso. Forty-five of the 166 villages in Kénédougou were randomly sampled and visited to assess livestock numbers, trypanosomosis risk, and tsetse challenge. The proportion of cattle infections associated with drug-resistant trypanosomes was assessed in the nine villages with the highest trypanosome infection prevalence and one village with a confirmed history of drug-resistant infections. These studies showed that resistance to both isometamidium and diminazene was widespread. However, there was considerable variation between villages in drug-resistance parameters, with the proportion of treated cattle with trypanosome infections 3 months after isometamidium prophylaxis varying from 6.9 to 63.8% and the proportion of cattle having infections 2 weeks after treatment with diminazene varying from 0 to 36.8%. The demonstration of widespread resistance to both isometamidium and diminazene has important implications, as administration of trypanocides is the most commonly employed method to control trypanosomosis in this area.