Download Epidemiology - Health - Lecture Slides and more Slides Public Health in PDF only on Docsity! *, Epidemiology of Andean
Yee Cutaneous Leishmaniasis
When my first class of Andean Cutaneous Leishmaniasis at the Universidad Peruana Cayetano Heredia finished, I was really impressed by the complexity of the epidemiology of this disease, and the efforts done to control the infection in Perú. Epidemiology of UTA is particularly interesting, because it represents the challenge of controlling, not just human, but animal factors, and the abundance of a vector like Lutzomyia. Moreover it’s also a consequence of the lack of modernity in some parts of the Peruvian Andes. Vectors in Perú • Lutzomyia peruensis (principal vector) • Lutzomyia ayacuchensis (in some areas) • Lutzomyia verrucarum (in some areas). Vectors. • Female sandfly enters the house to feed, in the intradomiciliary type of transmission, while most males sandflies remain outside. • They have limited flight range (they live close to the houses) . • They live in places with adequate humidity and temperatures (holes in trees, caves,etc). Range of arrival time of Lutzomya in Huanchoc-Peru (endemic village) • Lutzomyia verrucarum :6:40 pm - 9:40 pm. • Lutzomyia peruensis :6:50 pm - 9:40 pm. • Arrive earlier in June, July & August (specially cold < 9 C). • Arrive later in April & November ( > 9 C) Risk factors inside houses • Having a chimney (smoke repels sandflies) • Dry wood stored inside the house (provides resting holes for sandflies) • Holes in bedroom windows. Risk Factors around houses • Houses made of stone also provide resting holes for sandflies. • Unfinished house walls (no facing material), permits sandflies to enter more easily. (also could represent resting holes) Risk Factors around houses • Houses located close to creeks or waterways, provide low temperature, moderate humidity and enough flora for sandflies. Animals as risk factors of transmission • Which species are risk factors depend on vector preference. • The full role of domestic animals in UTA transmission is not clear understood. • Their evaluation is problematic because of the number of animals, and their patterns of behaviour. Age and transmission • No evidence for gender dependent risk was found , although there’s evidence that children are more affected than adults. Genetic Susceptibility • People infected at early age + recurrent lesions are more susceptible than those infected at a later age + single episode. Vector control. • Transmission can not be eliminated just by reducing sandfly abundance below a given threshold, but it can reduce the rate of transmission. Montenegro Skin Test (MST) • It’s an indirect method to diagnose leishmaniasis. Consists on applying an antigen (culture of promastigotes) intradermically. • The test’s results can be seen 48 - 72 hours later. MST (leishmanin test) • Sensitivity vary with dose, antigen type and storage condition. • Response to MST could be influenced by genetic variation. • MST could be positive by cross reacting infections (glandular TBC, leprosy, lizard Leishmaniasis) Clinical epidemiology • The majority of cases of recurrent disease are the result of relapses more than reinfection. Subclinical Infections • It’s not clear if they are due to low parasite virulence or dose or low human susceptibility. • Some may represent clinical infections with long incubation periods . Conclusions • House spraying can cause reduction in incidence but it does not provide a permanent solution. • Risk factors vary regionally for a single leishmania species (L.peruviana)
