Serological diagnosis of leishmaniasis: on detecting infection as well as disease

Abstract

SUMMARYSerological tests are very frequently used in epidemiological surveys of leishmaniasis and other parasitoses. Their sensitivity and specificity are generally defined with respect to parasitism and disease, rather than infection. The reason is that known positives are those individuals most likely to yield parasites, or who have distinctive clinical signs, and concomitantly high antibody titres. This paper investigates the performance of one serological method, the indirect fluorescent antibody test (IFAT), in detecting Leishmania infantum infection during an intensive 2-year cohort study of dogs in southern France. The results show that sensitivity and specificity with respect to infection can be simultaneously high, but maximum sensitivity is probably < 80%, and lasts for a relatively short period of 2-3 months after a lengthy incubation period. The IFAT gave the incidence of infection as 18-65% in the first year, whereas the best estimate of incidence based on parasite isolation and clinical observation was 72 %. But data from the second year suggest that the 72 % was itself an underestimate. We argue that, during epidemiological surveys, the IFAT in particular, and serological tests for leishmania in general, will underestimate prevalence, incidence and hence the scale of the control problem. However, there is evidence that tests for canine leishmaniasis employing high threshold titres will identify the most infectious animals, allowing selective treatment or culling of those which contribute disproportionately to transmission.

Leishmaniose canine dans le Rif (côte méditerranéenne marocaine) : enquête séro-épidémiologique

“…Selon Gradoni et al (1987) et Dye et al (1993), l'opé-ration de dépistage et d'élimination des animaux séro-positifs doit être effectuée juste avant la saison d'activité des phlébotomes. Cette mesure permettra de détecter les chiens qui ont été infectés pendant la saison précédente après qu'ils aient eu le temps de développer une séroconversion qui ne survient, en général, qu'après un délai de cinq mois après la période de transmission (Vidor et al, 1991).…”

Is the domestic dog (Canis familiaris) a reservoir host of American cutaneous leishmaniasis? A critical review of the current evidence.

“…Isolation and identification of parasites provides a conclusive but insensitive test for Leishmania infection in dogs, (i.e., there are many falsenegatives), and measurements of prevalence typically depend on less specific diagnostic tools (Table 2). [109][110][111][112][113][114] These include clinical (the detection of characteristic lesions or scars), parasitologic (usually by microscopic inspection of impression smears from lesions), and immunologic diagnosis (detection of a serologic or cell-mediated immune response). Table 2 lists reported studies that provide estimates of the prevalence of ACL in dogs surveyed in different endemic zones.…”

Leishmaniose visceral: estudo de flebotomíneos e infecção canina em Montes Claros, Minas Gerais

“…Estudos recentes da dinâmica de transmissão da LV, enfatizam duas variáveis a serem consideradas nos programas de controle: a sazonalidade da variação da população de flebotomíneos e o número de cães infectados 12 . Assim, este trabalho visa avaliar a situação da transmissão de LV do município de Montes Claros, através de inquérito sorológico canino, levantamento da fauna flebotomínica do município e do estudo do comportamento das espécies encontradas em relação à endofilia e exofilia.…”