Dermatobia hominis is a muscoid fly endemic to the Neotropical region. In Brazil, it is popularly known as mosca do berne. The larvae of this species cause cutaneous myiasis, also known as dermatobiasis, in a wide range of mammalian hosts, including humans. It is particularly important as a parasite of domestic animals, such as cattle and birds. Several wild animals are also infected1. Dermatobiasis is of considerable economic importance, since affected cattle produce poor quality leather, as well as less meat and milk2. In humans, the infections are painful but generally benign, even if the larvae reach maturity, but can be lethal in infants if the larvae penetrate the brain via the fontanelle3.
The females of D. hominis exhibit a characteristic reproductive behavior, namely, the use phoretic vectors to transmit their eggs to the host. This reproductive behavior was first recorded by Raphael Morales in Guatemala in 1911, and has subsequently been reported in several publications1,4. In general, these vectors are zoophilous Diptera, particularly calyptrate flies of the families Calliphoridae, Muscidae, Tabanidae, Fanniidae, Anthomyiidae, Sarcophagidae, Tipulidae, Syrphidae, Asilidae, Dolichopodidae, Drosophilidae, Ephydridae, Tachinidae, Otitidae, Stratiomyidae, and Trupaneidae. Among non-calyptrate flies, species of Simuliidae and Culicidae have been recorded as vectors1. In the latter, the genera Psorophora, Aedes, Mansonia, Haemagogus, Limatus, Onirion, Wyeomyia, Culex, Trichoprosopon, Johnbelkinia, and Anopheles have been recorded as phoretic vectors1,4–6.
Recent studies have reported new phoretic vectors of D. hominis2,7,8, which are generally calyptrate flies. In this note, we report for the first time the exploitation of Anopheles konderi, a dipterous non-calyptrate fly, as a phoretic vector of D. hominis.
During sorting of the specimens collected using CDC (Center for Disease Control) miniature light traps in July 2011 in Floresta Estadual do Trombetas [Sistema de Autorização e Informação em Biodiversidade (SISBIO) License Number 14054-3], Oriximiná municipality, Pará, Brazil (1°28′S; 56°22′W), a single female specimen of A. konderi, among several examined, was observed carrying eggs of D. hominis. The material was preserved in 80% ethanol and then carefully examined under a stereomicroscope (SV11; Zeiss) at ×66 magnification. As females of A. konderi are morphologically similar to those within the Anopheles oswaldoi complex9, the identification was molecularly confirmed by deoxyribonucleic acid (DNA) barcode analysis, using a 663-base pair region of the mitochondrial cytochrome oxidase subunit I (COI) gene. The specimen was photographed using a Celestron® model 44330 imaging system. The processes of sorting, microscopic analysis, taxonomic and molecular identification, and photography were conducted in the Laboratório de Genética de Populações e Evolução de Mosquitos Vetores de Malária e Dengue of Instituto Nacional de Pesquisas da Amazônia (INPA).
Eight eggs of D. hominis were found adhered to the ventral abdomen of the female A. konderi (Figure 1A, Figure 1B and Figure 1C), some of which had already hatched and were empty, whereas others were intact and contained visible larvae or were partially hatched. During handling of the material, some of the larvae became detached from their eggs (Figure 1D).
FIGURE 1 Anopheles konderi carrying the eggs and larvae of Dermatobia hominis: (A): and (B): Dorsal and ventral views, respectively, of a female A. konderi with eggs and partially hatched larvae attached to its abdomen (see arrows). (C):. Eggs of D. hominis attached to the abdomen of A. konderi. (D): Newly hatched larva of D. hominis. PHE: partially hatched eggs; UE:unhatched eggs; HE: hatched egg; A. : Anopheles; D.: Dermatobia .
Generally, a D. hominis female selects a phoretic vector that is of similar size to itself or smaller4,7, and the number of eggs deposited is directly proportional to the body size of the vector10. For example, in Fanniidae, a family of dipterous muscoids, an average of 16.4 eggs of D. hominis has been reported per vector specimen7. In our study, the number of eggs found on A. konderi corroborates this information. Compared with other dipterous muscoids with bulkier bodies, which are the main disseminators of D. hominis eggs, the anopheline mosquitoes are smaller and thinner6.
Understanding the epidemiology of dermatobiasis in the Neotropics depends on knowledge of the biological, ecological, and ethological parameters of phoretic vectors implicated in the transmission of the D. hominisectoparasite. To date, Anopheles konderi is the third species of Anopheles that has been reported as a phoretic vector of D. hominis, only preceded by A. boliviensis and A. intermedius1,4. Little is known about these parameters regarding A. konderi. This is mainly due to problems associated with the taxonomic status of this species. Anopheles konderi is morphologically similar to A. oswaldoi, with which it was synonymized in the past, although the males of these two species can be distinguished based on subtle differences in their genitalia. Subsequently, studies have reported that these two species differ in terms of their behavioral patterns and ITS2 (Internal Transcribed Spacer) and COI molecular markers, and also possibly as malaria vectors11,12. Currently, A. konderi is recognized as a distinct species from A. oswaldoi s.l., although it is a member of a group of cryptic species within the A. oswaldoi complex11–13.
Dermatobia hominis occurs primarily in forests, thereby avoiding dehydration and excessive heat14. Their phoretic vectors are predicted to have, among other characteristics, diurnal and zoophilic habits4,7. Specimens belonging to the A. oswaldoi complex have zoophilic behavior, generally inhabiting forests, but also show exophilic behavior9. Others have been observed to exhibit vespertine crepuscular and nocturnal activities, including biting humans, and it has been collected in human habitations15. As diurnal habit is one of the characteristics of D. hominis vectors, it is possible that the typically nocturnal A. konderi also has diurnal and/or crepuscular activities.
Although in the current study, we did not demonstrate that A. konderi routinely acts as a phoretic vector for the eggs of D. hominis, our observations indicate that this anopheline can potentially play this role, being one among the various dipteran species responsible for maintaining the incidence of dermatobiasis in wild animals.
