Updated results on atypical human trypanosomoses caused by animal trypanosomes

There are only two classical human forms of trypanosomoses, they are sleeping sickness in Africa (Trypanosoma brucei spp.) and Chagas' disease (T. cruzi) mainly in South America respectively. Other trypanosomes can infect a wide range of wild and domestic animals (fish, reptile, amphibians, mammals including cattle), but they are not supposed to be infective to human beings. However, several human cases infected by animal trypanosomes have been recently reported, in particular Trypanosoma lewisi (a Rattus trypanosome usually transmitted by fleas), and T. evansi (found for instance in cattle, camels, and mechanically transmitted by blood sucking insects such as tabanids or stomoxes). High density lipoprotein (HDL) in normal human serum (NHS) contains several compounds (e.g. ApoL-1) which protect us against African trypanosomes. The Indian patient infected with T. evansi reported in 2005 because of a genetic deletion was confirmed in the ApoL-1 gene in this patient, while another naturally T. evansi infected patient reported in Viet Nam in 2015 had a normal ApoL-1. The mode of transmission suspected in both cases was direct contamination via a wound while butchering raw beef. Both patients were cured successfully by using suramine, a drug for the acute form of sleeping sickness. Human infected with T. lewisi was mainly reported in babies. Although most of cases were transient infections, other required treatment or died. A recent case died from T. lewisi infection in India in 2015. It has been demonstrated that this parasite is resistant to NHS. Thus, T. lewisi is potentially a human pathogen or zoonotic pathogen. We present the new cases either described or suspected since the 2012, and previous cases as well (including infection by T. b. brucei, T. congolense). The problem of diagnosis and treatment will be considered, and the potential risk of emergence of a new zoonotic disease will be discussed

Standardisations internationale et régionale des épreuves immuno-enzymatiques : méthodes, intérêts et limites

Les techniques immuno-enzymatiques (enzyme-linked immunosorbent assay : ELISA) utilisées pour le diagnostic des maladies infectieuses ont fait l'objet de nombreuses études de standardisation visant une meilleure reproductibilité des tests, l'expression des résultats, le choix du seuil de positivité et des échantillons de référence. Il apparaît que la standardisation internationale des réactifs et des protocoles est nécessaire pour permettre les contrôles de qualité et la comparaison des résultats entre laboratoires, mais que l'interprétation des résultats peut se heurter à des différences importantes selon le secteur géographique étudié. Partant de ces travaux, et à la lumière du modèle de l'ELISA indirecte pour la recherche des anticorps dirigés contre #Trypanosoma vivax# chez les bovins, l'auteur propose de réaliser la standardisation internationale des réactifs, du protocole et du mode d'expression des résultats ELISA à l'aide d'échantillons de référence internationaux. En revanche, pour la standardisation locale, il est proposé de réaliser : l'échantillonnage des populations de référence locales ; l'établissement des fréquences de distribution des populations locales infectée et non infectée ; le choix de témoins représentatifs des populations locales (échantillons de référence secondaires) ; l'expression des résultats de la réaction par rapport à ces témoins ; l'établissement d'un contrôle interne de qualité fondé sur la réponse des témoins ; la détermination du seuil de positivité selon les exigences de l'utilisateur ; l'adaptation du seuil de positivité selon la prévalence observée dans le secteur géographique étudié. Ces mesures permettent de déterminer la sensibilité et la spécificité du test dans la population étudiée et, lorsque la prévalence de l'infection est connue, de calculer les valeurs prédictives du test. (Résumé d'auteur

Note sur des essais d'immunisation de lapins contre des tsé-tsé, Glossina fuscipes fuscipes (Diptera : Glossinidae)

L'immunisation de lapins contre les glossines a été tentée par injection d'intestins ou de jabots homogénéisés de mouches (Glossina fuscipes fuscipes ), avec l'adjuvant complet ou incomplet de Freund. L'effet des inoculations est évalué par le suivi de la mortalité et des capacités reproductrices de mouches alimentées sur ces lapins. Les résultats ne montrent qu'une augmentation, peu importante mais statistiquement significati ve, de la mortalité hebdomadaire dans les lots de glossines nourries sur les lapins immunisés par rapport aux témoins. (Résumé d'auteur

Cosmopolitan and neglected, stomoxys flies are important vectors of pathogens

The genus Stomoxys Geoffroy, 1762 includes 18 known species (Zumpt, 1973), 17 of which with a tropical distribution and one (S. calcitrans (L. 1758)) cosmopolitan. Stomoxys flies are haematophagous and are a nuisance because of their painful bites and blood predation, and they are also mechanical vectors of pathogens present in the blood and skin of their animal hosts, especially livestock and dogs but occasionally also humans. A phylogenetic analysis suggests the paraphyly of the genus Stomoxys, due to the inclusion of Prostomoxys saegerae in the group. The basal branching of S. indicus suggests an Oriental origin of the genus, around the end of the Oligocene. A phylogeographic study of S. calcitrans shows the presence of an Oriental lineage differentiated from the remainder. Stomoxys are not only immediate transmitters of pathogens, they are also suspected of delayed transmission by regurgitation of blood from crop or gut, which may considerably impact their role in the epidemiology of the transmitted diseases. Such a mechanism allows inter-herd transmission of pathogens. Equine infectious anemia, African swine fever, West Nile and Rift Valley viruses are known to be transmitted by Stomoxys, while others are suspected to be. Rickettsia (Anaplasma, Coxiella), as well as other bacteria and parasites (Trypanosoma spp., Besnoitia spp.), are also transmitted by Stomoxys. Finally, Stomoxys was also found to act as an intermediate host of the helminth Habronema microstoma and may be involved in the transmission of some Onchocerca and Dirofilaria species. Being cosmopolitan, S. calcitrans might have a worldwide and greater impact than previously thought on animal and human pathogen transmission. Based on a better knowledge of their role as nuisance species and their biology, new means of control of Stomoxys flies are currently under study to specifically attract these insects to traps or toxic targets

Field investigation of Trypanosoma evansi and comparative analysis of diagnostic tests in horses from Bahawalpur, Pakistan

In order to assess the prevalence of Trypanosoma evansi, a parasitological, molecular, and serological-based investigation was carried out in randomly sampled horses (n = 375) belonging to different age groups, sexes, and localities from the district of Bahawalpur, Pakistan. The diagnostic performance of applied tests was also compared. The prevalence was recorded as 0.5% with Woo's test, 1.3% with both ITS CF/BR PCR and RoTat 1.2 PCR, and 14.4% with CATT/T.evansi. Based on CATT/T.evansi, significant differences (P ≤ 0.05) were observed for prevalence estimates according to different localities, sexes, body condition scores, and origins. A nonsignificant difference (P ≥ 0.05) was observed among different age groups and variable parity numbers. Our study declares district Bahawalpur to be a high risk area for surra and proposes the potential use of CATT/T.evansi as a field test of choice for surveys in horses. However, the status of seropositive animals should be confirmed using a more sensitive molecular tool such as the satellite DNA target. A widespread status of anti-Trypanosoma antibodies calls for control measures and further investigation of various species (camels, cattle, sheep, goats, buffaloes) inhabiting the same area to identify reservoir status. (Résumé d'auteur

Evaluation de la sensibilité du test de Woo pour la détection de Trypanosoma vivax

L'objet du présent travail a été de chiffrer la sensibilité de la technique de Woo pour la détection de Trypanosoma vivax de Guyane, en l'éprouvant sur des échantillons sanguins de parasitémie déterminée, allant de 1 à 1 767 trypanosomes/ml, préparés par dilution de sang infecté dans du sang non infecté. L'expérience a été réalisée avec du sang de mouton. Une technique simple est décrite, pour le dénombrement des parasites dans le sang. Le seuil moyen de positivité du test de Woo chez le mouton a été d'environ 200 ± 110 T. vivax/ml. Le test a présenté une sensibilité de 100 p. 100 quand la parasitémie était supérieure à 700 parasites/ml, environ 80 p. 100 entre 300 et 700, 50 p. 100 entre 60 et 300, puis sa sensibilité a été quasi nulle en-deçà de 60 parasites/ml. Des indices sont fournis, permettant de quantifier la parasitémie en fonction du nombre de parasites observés entre lame et lamelle (parasitémie > 2 000), ou dénombrés dans le tube à hématocrite (parasitémie < 2 000). Il est proposé d'évaluer la sensibilité des techniques visant à mettre en évidence une infection active, par rapport à des références fixes, en l'occurence, des parasitémies connues, créées artificiellement, comme il l'a été décrit. (Résumé d'auteur

Atypical human infections by animal trypanosomes: evaluation of human and animal trypanocidal drugs against Trypanosoma lewisi in Wistar rats

Trypanosomosis is a disease of medical and veterinary importance, mainly distributed in tropical areas of Africa, Latin America and Asia. Some Trypanosoma species are typically pathogenic for animals, such as Trypanosoma vivax, T. congolense, T. evansi etc, and others are zoonotic, such as the agents of sleeping sickness in Africa (Trypanosoma brucei ssp.), or Chagas disease in Latin America (T. cruzi). Beside these 2 “typical” human trypanosomes, there is a growing number of reported “atypical” human infections due to Trypanosoma evansi, a livestock parasite, or Trypanosoma lewisi, a rat commensal, especially in Asia. Drugs available for the treatment of T. brucei ssp in humans are obviously of choice for the control of T. evansi because it is derived from T. brucei lineage; indeed, in 2 recent cases of human infection by T. evansi, successful treatments were obtained using suramine. However, concerning T. lewisi, there is a need to determine the efficacy of trypanocidal drugs for the treatment in humans. In a recent study, pentamidine and fexinidazole were shown to have the best efficacy against one stock of T. lewisi in rats, they have thus been explored amongst others. In order to explore efficient trypanocidal drugs, attempts were made to treat groups of 3 rats experimentally infected by T. lewisi, using low and high doses of the available human and veterinary trypanocidal drugs: diminazen aceturate (DA; 14 and 28 mg/kg), isometamidium chloride (IMC: 2 and 4 mg/kg), quinapyramine sulfate and chloride (QSC; 8.3 and 16.6 mg/kg), cymelarsan (Cym; 0.5 and 1 mg/kg), suramine (20 and 40 mg/kg), pentamidine diisetionate (Pt: 8 and 16 mg/kg), eflornitine hydrochloride (Efl; 800 and 16000 mg/kg), nifurtimox (Nt; 30 and 60mg/kg), benznidazole (Bz; 20 and 40 mg/kg) and fexinidazole (Fex; 200 mg/kg). At the exception of Nt, Bz and Fex which were administered perorale route, all drugs were intramuscularly injected. All treatments at all doses failed to clear parasites from rat's blood. To confirm the potential efficacy of fexinidazole, a mixed infection protocol was set up in cyclophosphamide immunosuppressed rats. Animals were infected successively by T. lewisi and T. evansi, and received 10 daily peroral administrations of 200 mg/kg fexinidazole or 0.5 mg/kg Cym. T. evansi was cleared from the rat's blood within 24 to 48 hours; however, the treatment did not affect T. lewisi which remained in high number in the blood until the end of the experiment. Results are discussed and further studies suggested. Because of its potential as an emerging parasite in humans, identifying efficient trypanocides against T. lewisi is required