Medical and Veterinary Entomology (1992) 6, 195-200
Host preferences of the phlebotomine sandfly Lutzomyia longipalpis in Amazonian Brazil R . J . Q U I N N E L L , C . D Y E and J . J . S H A W ” DepartmentofMedicalParasitology, London School of Hygiene and Tropical Medicine, and *Wellcome Parasitology Unit, Instituto Evandro Chagas, C.P. 3, BelCm, 66001 Para, Brazil Abstract. Experiments were undertaken to determine the relative attractiveness of.humans, dogs and chickens to Lutzomyia longipalpis, the principal vector of Leishmania chagasi causing American visceral leishmaniasis. Field experiments in two villages on Maraj6 Island, Para State, Brazil, showed that one boy attracted significantly more flies than one dog or chicken, and slightly fewer flies than a group of six chickens. Experiments with laboratory-bred female flies showed that a significantly greater number of flies engorged on a single human than on either a single dog or chicken, and man-biting catches demonstrated the willingness of flies to bite in the field. It appears that Lu.longipalpis has catholic feeding habits, the attractiveness of different hosts being largely a function of their relative sizes. These results are discussed with reference to the epidemiology of visceral leishmaniasis in Brazil.
Key words. Lutzomyia longipalpis, Phlebotominae, sandfly, host preference, visceral leishmaniasis, Leishmania chagasi, Amazonia, Brazil. Introduction
The phlebotomine sandfly Lutzornyia Iongipalpis Lutz & Neiva (Diptera: Psychodidae) is the most important vector of American visceral leishmaniasis (AVL), caused by Leishmania chagasi Cunha & Chagas (Lainson et al., 1977; Lewis & Ward, 1987). In most areas it is the only known vector, although Lu.evansi is an alternate vector in Colombia (Travi et al., 1990). Although AVL occurs from Mexico to Argentina (Grimaldi et al., 1989), over 90% of human cases come from Brazil. Within Brazil there are large regional differences: of 9295 cases reported during 1983-88, 8740 were from the northeast and only 193 from the Amazon region (Vieira et al., 1990). AVL is thought to be largely zoonotic, the most important reservoir hosts being the domestic dog and various wild canids, especially Cerdocyon thous (L.) (Deane, 1956; Lainson et al., 1990). Prevalence of infection is generally greater in dogs than in humans (Deane, 1961), although few surveys have used comparable techniques in both populations. In Brazil Lu.longipalpis is often abundant peridomestically, especially in animal pens (Deane, 1956). It has Correspondence: Dr C. Dye, Vector Biology and Epidemiology Unit, Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street, London WClE 7HT, U.K.
also been found in smaller numbers in some forest areas (Lainson et al., 1990). Despite its abundance, very little is known of its innate host preferences or its actual biting behaviour. In northeast Brazil, e.g. Cear5 State, Lu.longipalpis is considered to be anthropophilic, readily biting man (Deane & Deane, 1962; Ward et al., 1983). Deane (1956) captured more flies on people than on dogs, although the largest numbers were caught on donkeys, and up to 2608 Lu.longipalpis females have been captured inside a single house (Deane & Deane, 1962). In Costa Rica, Zeledon et al. (1984) captured similar numbers of flies on people, dogs, pigs, horses and cattle. By contrast, in Amazonian Brazil, casual observations suggest -that Lu.longipalpis is ‘not particularly anthropophilic, and much more inclined to feed on dogs’ (Lainson & Shaw, 1979). In Rio de Janiero State, Aguiar etal. (1987) captured more flies on chickens than either people or dogs. Corredor et al. (1989) made night biting collections in Colombia and ‘observed repeatedly that [Lu.longipalpis] prefer to feed on domestic animals, including poultry, if these animals are available.’ None of these studies amount to definitive field experiments on host choice by Lu.longipalpis females resolving the questions of (1) whether or not they have host preferences, either innate or facultative; if so (2) whether host preferences vary from one population to another. Such variation might be expected, as Lu. longipalpis, sen.su lato, is known to exist as a complex of at least two species, 195
196
K. J . Quirinell, C. Dye arid J . J. Shaw
which are reproductively isolated from each other and which produce different pheromone compounds (Ward et a [ . , 1983, 1988). Both species occur in NE and S Brazil, while only one occurs in the Amazon region. and it has been suggested that interspecific differences in the degree of anthropophily may help explain the distribution of human AVL disease in Brazil (Ward et al., 1983, 1985). In this paper we focus on question (1) above, reporting the results of a series of experiments designed to determine the innate host preferences of Lu.longpu1pi.s on Maraj6 Island in Amazonian Brazil. Three host species were used: humans, dogs and chickens, the latter being the most abundant domestic animal in the region. The work is the first step towards explaining why, on Marajo Island. seroprevalence of AVL in the human population is very much lower (
Host preferences of the phlebotomine sandfly Lutzomyia longipalpis in Amazonian Brazil R . J . Q U I N N E L L , C . D Y E and J . J . S H A W ” DepartmentofMedicalParasitology, London School of Hygiene and Tropical Medicine, and *Wellcome Parasitology Unit, Instituto Evandro Chagas, C.P. 3, BelCm, 66001 Para, Brazil Abstract. Experiments were undertaken to determine the relative attractiveness of.humans, dogs and chickens to Lutzomyia longipalpis, the principal vector of Leishmania chagasi causing American visceral leishmaniasis. Field experiments in two villages on Maraj6 Island, Para State, Brazil, showed that one boy attracted significantly more flies than one dog or chicken, and slightly fewer flies than a group of six chickens. Experiments with laboratory-bred female flies showed that a significantly greater number of flies engorged on a single human than on either a single dog or chicken, and man-biting catches demonstrated the willingness of flies to bite in the field. It appears that Lu.longipalpis has catholic feeding habits, the attractiveness of different hosts being largely a function of their relative sizes. These results are discussed with reference to the epidemiology of visceral leishmaniasis in Brazil.
Key words. Lutzomyia longipalpis, Phlebotominae, sandfly, host preference, visceral leishmaniasis, Leishmania chagasi, Amazonia, Brazil. Introduction
The phlebotomine sandfly Lutzornyia Iongipalpis Lutz & Neiva (Diptera: Psychodidae) is the most important vector of American visceral leishmaniasis (AVL), caused by Leishmania chagasi Cunha & Chagas (Lainson et al., 1977; Lewis & Ward, 1987). In most areas it is the only known vector, although Lu.evansi is an alternate vector in Colombia (Travi et al., 1990). Although AVL occurs from Mexico to Argentina (Grimaldi et al., 1989), over 90% of human cases come from Brazil. Within Brazil there are large regional differences: of 9295 cases reported during 1983-88, 8740 were from the northeast and only 193 from the Amazon region (Vieira et al., 1990). AVL is thought to be largely zoonotic, the most important reservoir hosts being the domestic dog and various wild canids, especially Cerdocyon thous (L.) (Deane, 1956; Lainson et al., 1990). Prevalence of infection is generally greater in dogs than in humans (Deane, 1961), although few surveys have used comparable techniques in both populations. In Brazil Lu.longipalpis is often abundant peridomestically, especially in animal pens (Deane, 1956). It has Correspondence: Dr C. Dye, Vector Biology and Epidemiology Unit, Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street, London WClE 7HT, U.K.
also been found in smaller numbers in some forest areas (Lainson et al., 1990). Despite its abundance, very little is known of its innate host preferences or its actual biting behaviour. In northeast Brazil, e.g. Cear5 State, Lu.longipalpis is considered to be anthropophilic, readily biting man (Deane & Deane, 1962; Ward et al., 1983). Deane (1956) captured more flies on people than on dogs, although the largest numbers were caught on donkeys, and up to 2608 Lu.longipalpis females have been captured inside a single house (Deane & Deane, 1962). In Costa Rica, Zeledon et al. (1984) captured similar numbers of flies on people, dogs, pigs, horses and cattle. By contrast, in Amazonian Brazil, casual observations suggest -that Lu.longipalpis is ‘not particularly anthropophilic, and much more inclined to feed on dogs’ (Lainson & Shaw, 1979). In Rio de Janiero State, Aguiar etal. (1987) captured more flies on chickens than either people or dogs. Corredor et al. (1989) made night biting collections in Colombia and ‘observed repeatedly that [Lu.longipalpis] prefer to feed on domestic animals, including poultry, if these animals are available.’ None of these studies amount to definitive field experiments on host choice by Lu.longipalpis females resolving the questions of (1) whether or not they have host preferences, either innate or facultative; if so (2) whether host preferences vary from one population to another. Such variation might be expected, as Lu. longipalpis, sen.su lato, is known to exist as a complex of at least two species, 195
196
K. J . Quirinell, C. Dye arid J . J. Shaw
which are reproductively isolated from each other and which produce different pheromone compounds (Ward et a [ . , 1983, 1988). Both species occur in NE and S Brazil, while only one occurs in the Amazon region. and it has been suggested that interspecific differences in the degree of anthropophily may help explain the distribution of human AVL disease in Brazil (Ward et al., 1983, 1985). In this paper we focus on question (1) above, reporting the results of a series of experiments designed to determine the innate host preferences of Lu.longpu1pi.s on Maraj6 Island in Amazonian Brazil. Three host species were used: humans, dogs and chickens, the latter being the most abundant domestic animal in the region. The work is the first step towards explaining why, on Marajo Island. seroprevalence of AVL in the human population is very much lower (
