Cette etude consacree aux trypanosomoses affectant le betail en Amerique latine, la premiere du genre, dresse un bilan complet de la situation entre 1990 et 1995 qui servira de reference pour toutes les etudes et comparaisons a venir. L'auteur evalue le role et les effets nocifs des vecteurs mecaniques, en mettant l'accent sur les dommages infliges par les Tabanides ; l'impact de ces vecteurs sur l'elevage est analyse a la lumiere d'indications statistiques. Ces donnees justifient amplement l'adoption de strategies saisonnieres de prophylaxie contre ces insectes dont les effets sur l'elevage, bien que localises et de courte duree, ont ete jusqu'a present sous-estimes. Le modele d'analyse epidemiologique de la trypanosomose bovine transmise par des vecteurs mecaniques presente dans cet ouvrage s'applique non seulement a l'Amerique latine mais aussi a certaines regions d'Afrique ou le recul des populations de glossines a permis d'eradiquer la trypanosomose transmise par ces vecteurs biologiques. L'analyse des outils diagnostiques et des methodes de prophylaxie des trypanosomoses s'applique aussi bien a l'Amerique, a l'Afrique qu'a l'Asie. De meme, les informations sur les trypanosomoses transmises par des vecteurs mecaniques composent un modele pertinent pour nombre de regions du globe

Livestock Trypanosomoses and Their Vectors in Latin America

Tsetse flies (Diptera: Glossinidae) are vectors of several species of pathogenic trypanosomes in tropical Africa. Human African trypanosomiasis (HAT) is a zoonosis caused by Trypanosoma brucei rhodesiense in East Africa and T. b. gambiense in West and Central Africa. About 100 000 new cases are reported per year, with many more probably remaining undetected. Sixty million people living in 36 countries are at risk of infection. Recently, T. b. gambiense trypanosomiasis has emerged as a major public health problem in Central Africa, especially in the Democratic Republic of Congo, Angola and southern Sudan where civil war has hampered control efforts. African trypanosomes also cause nagana in livestock. T. vivax and T. congolense are major pathogens of cattle and other ruminants, while T. simiae causes high mortality in domestic pigs; T. brucei affects all livestock, with particularly severe effects in equines and dogs. Central to the control of these diseases is control of the tsetse vector, which should be very effective since trypanosomes rely on this single insect for transmission. However, the area infested by tsetse has increased in the past century. Recent advances in molecular technologies and their application to insects have revolutionized the field of vector biology, and there is hope that such new approaches may form the basis for future tsetse control strategies. This article reviews the known biology of trypanosome development in the fly in the context of the physiology of the digestive system and interactions of the immune defences and symbiotic flora.

Interactions between tsetse and trypanosomes with implications for the control of trypanosomiasis.

Studies of host‐parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium , in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.

http://userwww.sfsu.edu/sehgal/Publications_files/Trypanosomes%20Sehgal.pdf

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

In a sleeping sickness focus of Cote d'Ivoire, trypanosomes were characterized in humans, pigs and tsetse using various techniques. Out of 74 patients, all the 43 stocks isolated by KIVI (Kit for In Vitro Isolation) appeared to belong to only one zymodeme of Trypanosoma brucei gambiense group 1 (the major zymodeme Z3). The only stock isolated on rodents belonged to a different, new, zymodeme (Z50), of T. b. gambiense group 1. From 18 pigs sampled in the same locations as the patients, PCR showed a high proportion of mixed infections of T. brucei s. l. and T. congolense riverine-forest. Zymodemes of T. brucei s. l. from these pigs were different from those found in humans. From a total of 16 260 captured tsetse (Glossina palpalis palpalis), 1701 were dissected and 28% were found to be infected by trypanosomes. The most prevalent trypanosome was T. congolense riverine-forest type, followed by T. vivax, T. bruceis. l. and T. congolense savannah type, this latter being associated to the forest type of T. congolense in most cases. Mixed infections by 2 or 3 of these trypanosomes were also found. Use of a microsatellite marker allowed us to distinguish T. b. gambiense group 1 in some of the mature infections in tsetse. Differences in infection rates and in trypanosome genotypes according to the host might indicate that the pig may not be an active animal reservoir for humans in this focus.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182004005876

Mixed infections of trypanosomes in tsetse and pigs and their epidemiological significance in a sleeping sickness focus of Côte d'Ivoire.

The use of specific and generic primers to identify trypanosome infections of wild tsetse flies in Tanzania by PCR

http://www.sleeping-sickness.ird.fr/pdf/0011.pdf

Detection and identification of trypanosomes by polymerase chain reaction in wild tsetse flies in Cameroon

The polymerase chain reaction (PCR) method was used to characterize trypanosome infections in tsetse flies from 3 sleeping sickness foci in Cameroon. The predominant tsetse species found was Glossina palpalis palpalis. An average infection rate of 12.1% was revealed by microscopical examination of 888 non-teneral tsets flies. PCR amplification analyses for trypanosome identification were carried out on 467 flies, with primer sets specific for Trypanosoma (Trypanozoon) brucei s.1., T. (Duttonella) vivax, T. (Nannomonas) simiae and forest type T. (Nannomonas) congolense. Of 467 flies 93 were positive by microscopical analysis while PCR succeeded in identifying 89 positive flies. Of the PCR-positive flies 34 (38.2%) were negative by microscopical examination. PCR amplification, when compared to the parasitological technique, gave a higher estimate of infection rate of trypanosomes in natural tsetse populations. The PCR technique did, however, fail to identify 40.9% (38/93) of the parasitologically positive flies. The reasons for this failure are discussed. The overall prevalence of mixed infections, assessed by PCR, was 37.1%; the majority (72.7%) involved T. brucei and forest type T. congolense.

Characterization of trypanosome infections by polymerase chain reaction (PCR) amplification in wild tsetse flies in Cameroon

/pdf/utilisation-de-la-pcr-sur-sang-pour-le-diagnostic-des-1blawj5hc3.pdf

Utilisation de la PCR sur sang pour le diagnostic des trypanosomoses porcines

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Detection and identification of trypanosomes by polymerase chain reaction in wild tsetse flies in Cameroon

Characterization of trypanosome infections by polymerase chain reaction (PCR) amplification in wild tsetse flies in Cameroon

Utilisation de la PCR sur sang pour le diagnostic des trypanosomoses porcines