Visceral leishmaniasis in Teresina, state of Piauí, Brazil: preliminary observations on the detection and transmissibility of canine and sandfly infections

Abstract

A Leishmania donovani-complex specific DNA probe was used to confirm the widespread dissemination of amastigotes in apparently normal skin of dogs with canine visceral leishmaniasis. When Lutzomyia longipalpis were fed on abnormal skin of five naturally infected dogs 57 of 163 (35%) flies became infected: four of 65 flies (6%) became infected when fed on apparently normal skin. The bite of a single sandfly that had fed seven days previously on a naturally infected dog transmitted the infection to a young dog from a non-endemic area. Within 22 days a lesion had developed at the site of the infective bite (inner ear): 98 days after infection organisms had not disseminated throughout the skin, bone marrow, spleen or liver and the animal was still serologically negative by indirect immunofluorescence and dot-enzyme-linked immunosorbent assay. When fed Lu. longipalpis were captured from a kennel with a sick dog known to be infected, 33 out of 49 (67%) of flies contained promastigotes. In contrast only two infections were detected among more than 200 sandflies captured in houses. These observations confirm the ease of transmissibility of L. chagasi from dog to sandfly to dog in Teresina. It is likely that canine VL is the major source of human VL by the transmission route dog-sandfly-human. The Lmet2 DNA probe was a useful epidemiological tool for detecting L. chagasi in sandflies.

The Effect of Removing Potentially Infectious Dogs on the Numbers of Canine Leishmania infantum Infections in an Endemic Area with High Transmission Rates

“…Moreover, not all infected dogs were expected to be detected using serology, 9 as the DPP CVL rapid test has a low sensitivity (47%) in identifying parasite-positive dogs that do not manifest clinical signs of VL. 23 However, despite the infectious potential of naturally infected asymptomatic seropositive dogs for sand flies, 29,30 these dogs are likely not epidemiologically significant. It is known that the probability of L. longipalpis becoming infected from an infected dog significantly increases with the strength of the dog's anti-Leishmania antibody response and its total clinical score.…”

Presença de animais associada ao risco de transmissão da leishmaniose visceral em humanos em Belo Horizonte, Minas Gerais

“…Esta associação entre a infecção humana e a presença de cães foi, também, verificada por Vexenat et al (1994); Paranhos- Silva et al (1998) e Costa e Vieira (2001), que atribuíram este aumento do risco ao intenso parasitismo dérmico desses protozoários nos cães.…”

“…Porém, tais ações ainda não minimizaram o número de casos humanos e caninos na cidade. Historicamente, em Belo Horizonte, as taxas de letalidade da população humana chegaram a atingir média de 13% no período de 1994de -2004de (Borges, 2006Leishmaniose..., 2006). O conhecimento mais apurado das associações entre doença e seus fatores determinantes tem auxiliado no direcionamento e na priorização de estratégias no controle de muitas enfermidades.…”

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

“…162 These infection rates can be compared with those on ZVL-infected dogs: 13 of 16 naturally L. infantum-infected, seropositive dogs were infectious to Phlebotomus perniciosus fed on the head, with a mean infection rate of 37% (149 of 404). 163 Studies on dogs either naturally or experimentally infected with L. infantum or L. chagasi have shown that 1) asymptomatic dogs can be infectious to sand flies; 162,164,165 (2) dogs become infectious to sand flies after a median period of about 200 days; 31 3) infectiousness may be associated with high antibody titers; 162 and 4) the infectiousness of dogs that have serologically recovered and/or clinically healed after treatment tends to decrease temporarily until the dogs relapse. 164,166 Whether any of these features are true for ACL is unknown.…”