A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Fly Saliva

Leishmania braziliensis is found in Central and South America and is transmitted through the bite of a sand fly. This parasite is dangerous because L. braziliensis causes mucocutaneous leishmaniasis that cause disfiguring lesions of the nose, mouth, and other areas of the body with mucous membranes (Samuelson et al. 1991). Sand flies are carriers of multiple species of Leishmania parasites; one being L. braziliensis. When a sand fly bites a mammal for a blood meal, the sand fly salivates into the skin and transmits L. braziliensis by injecting epimastigotes. The saliva of a sand fly is thought to enhance the transmission of Leishmania species due to the saliva of the sand fly containing several substances that include a vasodilator, which is a substance that widens the blood vessels increasing blood flow (Samuelson et al. 1991).  Samuelson et al (1991) sought to confirm if sand fly saliva does effect Leishmania transmission by looking at L. braziliensis infection in mice.

In order to test if sand fly saliva does effect Leishmania transmission, a strain of L. braziliensis was isolated from a human patient and was cultured on blood agar plates. The test animals for this study were BALB/c mice, which are laboratory-bred albino house mice. Groups of five mice were injected in the hind footpad with the cultured L. braziliensis and other groups of mice were injected with L. braziliensis that was mixed with one salivary gland of a sand fly. When lesions developed, the thickness of the lesion was measured as well as an uninfected hind footpad (Samuelson et al. 1991). After several months, the mice were killed and the number of parasites found within the lesions was measured.

The results of this study showed L. braziliensis caused faster progressive cutaneous lesions in mice when injected with the contents of sand fly saliva. Parasites that had been injected with sand fly saliva produced large and rapidly growing cutaneous nodules (Samuelson et al. 1991). Lesions in the mice caused by L. braziliensis injected with sand fly saliva were also found to have 5,000-fold more parasites than the hosts injected with parasites without sand fly saliva.

 

This article relates to the study by Gabriel et al. (1992) “Description of Leishmania equatorensis sp. n. (Kinetoplastida: Trypanosomatidae), A New Parasite Infecting Arboreal Mammals in Ecuador” because Gabrial et al. (1992) found Leishmania braziliensis and Leishmania equatorensis are indistinguishable in behavior and appearance and are almost identical in their enzymatic profile. However, L. braziliensis can infect humans unlike L. equatorensis. Due to the lack of studies performed on L. equatorensis, L. braziliensis was chosen for my future articles because of their structural similarities.

Citation

J. Samuelson, E. Lerner, R. Tesh, R. Titus, 1991, A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Fly Saliva, J. Exp. Med. Sci. 173(1): 49-54

-Kaitlin Smith (Revised 11/29/12)