Rhesus monkey model for Leishmania major transmitted by Phlebotomus papatasi sandfly bites

Abstract

Leishmaniasis research needs a near-human model for investigations of natural infection processes, immunological responses and evaluation of treatments. Therefore, we developed a reproducible system using Leishmania major Yakimoff & Schokhor (Trypanosomatidae: Kinetoplastida), the cause of Old World zoonotic cutaneous leishmaniasis (ZCL), transmitted to rhesus monkeys Macaca mulatta (Zimmerman) (Primates: Cercopithecidae) by sandfly bites of experimentally infected Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae). Eight monkeys of presumed Indian origin (Leishmania naive) were exposed to bites of female sandflies that had been infected with L. major by membrane-feeding on human blood seeded with amastigotes isolated from hamster footpad lesions. Infection rates of membrane-fed sandflies averaged > 85% seven days after the infective feed, with uniformly high numbers of promastigotes in the stomodaeal valve region of the sandfly gut. Nodules and ulcerating dermal lesions developed on 7/8 monkeys 2-4 weeks post-bite and persisted for 3-7 months. Monkeys also developed satellite lesions beyond the area of sandfly bites on the head, but not on the chest. Three re-challenged monkeys developed lesions that healed faster than lesions from their primary challenges. After infection, monkeys developed delayed type hypersensitivity (DTH) responses to a panel of Leishmania skin test antigens (LSTA) and, when tested by ELISA and IFA, showed significant post-infection antibody titres which typically rose for approximately 170 days and then gradually receded during the next 100 days following the first challenge. After the second challenge, antibody titres spiked higher within approximately 50 days and receded more rapidly. In contrast, four rhesus macaques of Chinese origin developed no lesions following infected sandfly bites, although they raised antibodies and LSTA reactions, indicating subclinical infection.

Poor Vector Competence of Fleas and the Evolution of Hypervirulence inYersinia pestis

“…The vector competence of fleas is low, compared with those characterized for mosquito, sandfly, and tick vectors of other pathogens [38][39][40][41][42], which may be a reflection of the recent transition of Y. pestis to arthropodborne transmission. With a longer coevolutionary history, Y. pestis strains better able to colonize fleas and with a lower threshold of infection may evolve.…”

A sand fly salivary protein vaccine shows efficacy against vector-transmitted cutaneous leishmaniasis in nonhuman primates

“…Vector transmission results in a higher inoculum variability compared to needle injection, because infected flies egest a variable number of parasites (30-32) and their feeding/probing behavior is uneven. This was overcome by using 50 Leishmania-infected P. duboscqi sand flies that resulted in a 90% successful infection rate, an improvement over previous reports of infection rates in NHP after vector transmission of L. major (33). The use of 50 infected flies resulted in clusters of lesions that resembled human CL evolving from nodules to papules to ulcerated lesions with elevated borders and a necrotic center before self-healing over the course of 14 weeks.…”

“…Because of reports of enhanced resistance to CL in rhesus monkeys of Chinese origin, we used NHP of Indian origin that have been shown to be susceptible to L. major parasites (33). All NHP were screened for good physical health and absence of antibodies reactive to P. duboscqi sand fly salivary proteins before enrollment into the animal protocol.…”

Comparative fecundity and survival rates of Phlebotomus papatasi sandflies membrane fed on blood from eight mammal species

“…Even so, the routine use of membrane‐feeders in mass‐rearing of standard sandfly colonies should bring substantial savings in costs of animal care, with the bonus of animal welfare. However, we recommend direct feeding of sandflies on suitable hosts periodically (say every fifth generation), to ensure that they do not lose the ability to bite live animals, which may be needed for transmission studies (Probst et al ., 2001).. It would be advantageous to design a larger self‐warming membrane‐feeder that can be introduced directly to sandflies in their colony cage.…”