Volume 8, Number 12—December 2002
Perspective
Role of the Domestic Chicken (Gallus gallus)in the Epidemiology of Urban Visceral Leishmaniasis in Brazil
Bruce Alexander*
, Renata Lopes de Carvalho†, Hamish McCallum‡, and Marcos Horácio Pereira§
, Renata Lopes de Carvalho†, Hamish McCallum‡, and Marcos Horácio Pereira§
Table
Positive and negative factors associated with chicken raising that may affect the transmission of Leishmania infantum by Lutzomyia longipalpis in urban foci of zoonotic visceral leishmaniasis, Brazil
| Factors affecting risk of transmission of Le. infantum to humans (all+) | Factors affecting risk of infection of Lu. longipalpis by Le. infantum (all-) | Factors affecting maintenance of sand fly populations (+/-) |
||
|---|---|---|---|---|
| Facilitation of blood feeding (+) | Nutrition (-) | Bringing sexes together (+) | ||
| Chicken rearing seen by local people as providing several benefits not directly related to Leishmania transmission, e.g., scorpion control, source of food and income and keeping yards free of trash Odor and CO2 emitted by chickens attract infected sand flies to the vicinity of human dwellings Presence of chickens attracts potential reservoirs of Le. infantum to the vicinity of human dwellings where sand flies also present Dogs kept to guard chicken houses from thieves and predators are themselves potential reservoirs of Le. Infantum Chicken houses may act as resting sites for engorged sand flies No evidence that chicken houses act as sand fly breeding sites although associated rodent burrows might be exploited | Complement levels in blood fatal to Leishmania? Temperature of chicken blood too high (41°C) to permit growth of Leishmania Greater facility with which sand flies can feed on chickens would favor biting by infected sand flies whose capacity to ingest blood is compromised by blockage of the pharynx? Nucleated erythrocytes in blood meal stimulate DNAase activity fatal to Leishmania within sand fly gut? | Chicken RBCs soft and easily ruptured Chickens easier to feed on by sand flies that have pharynx partially blocked by Leishmania? Chicken skin thinner than that of mammals (0.02 mm), esp. on feathered areas of body Thrombocytes less efficient than mammalian platelets in preventing blood loss | Protein content of chicken plasma considerably lower than that of mammals Nucleated blood cells have 31 times DNA content of human erythrocytes; elimination associated w/ problems of water balance? Hematocrit value of chicken blood about 50% that of mammals; sand flies cannot concentrate blood meal during engorgement | CO2 and odor attractive to both males and females High chicken body temperature might favor dissemination of pheromone Passivity of roosting chickens lets male sand flies display relatively undisturbed |
aRBCs, red blood cells; esp., especially.
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