Human pseudomyiasis caused by Eristalis tenax (Linnaeus) (Diptera: Syrphidae) in Goiás

Abstract

The objective of the present work was to register the first proven cases of human pseudomyiasis due to Eristalis tenax in Goiás State, Brazil, underscoring their clinical manifestations and direct relationship with hygiene. The taxonomic identification of the instars was done according to the descriptions and keys presented by James (1947), Hartley (1961) and Guimarães & Papavero (1999 James (1947), Hartley (1961) e Guimarães & Papavero (1999 Gastrointestinal myiasis caused by the cosmopolitan drone fly Eristalis tenax (Diptera: Syrphidae) is classified as pseudomyiasis, given the biology of the fly and that it occurs in an accidental manner. Its presence, in the surface of the digestive tract is responsible for the pathologic physiology, in general of lesser gravity than that caused by the obligatory or facultative parasites 6 . RESUMO O presente trabalho visa registrar os primeiros casos evidenciados de pseudomiíases humanos por Eristalis tenax no estado de Goiás, Brasil, destacando suas manifestações clínicas e suas relações diretas com os hábitos higiênicos. A identificação taxonômica das larvas foi realizada com base nas descrições e chaves apresentadas porThe genus Eristalis (Linnaeus) was designated commonly as Tubifera (Meigen), and some researchers have also denominated it Eristalomyia. The simple observation of the family rat-tailed maggot (long respiratory siphon) characteristic in larvae instars has incited some researchers to the diagnosis of E. tenax. Though, this is not a pathognomonic characteristic, or exclusive to this species or its genus. Thus, many incorrect records and inaccurate descriptions result from this extrapolation 3 .The larvas of E. tenax are extremely resistant to adverse conditions of pressure, heat and salinity 5 . They live in water polluted by feces, sewage, liquid excrements and organic materials in decomposition, including carcasses. Occasionally they can be found in relatively clean water 3 , however, the occurrence of E. tenax larvae in stagnated waters indicates a high degree of pollution 1 .Gastrointestinal pseudomyiasis presents unspecific symptoms and its clinical aspects vary in agreement with the 186

Gastrointestinal symptoms resembling ulcerative proctitis caused by larvae of the drone flyEristalis tenax

“…Thereafter, it is believed that the transformation of mature larvae into pupae indeed occurs externally. 15 Since human infestations due to E. tenax larvae have been probably neglected up so far, only 40 cases have been reported (including our case report) ( Table 1). The degree and presence of symptoms, mostly non-specific, likely depended on the parasite burden, ranging from diarrhoea and abdominal pains The imago resembles a honeybee, but has only two wings, and exhibits no sting.…”

“…The most obvious point of entry appears as the ingestion of eggs or immature larvae in contaminated food or drink. 3,14,15 The other point of accidental entry was hypothesized by Fritz KE Zumpt: according to him, the female E. tenax may lay eggs on the anal margin, e.g. at the time of defecation in the wild, and the hatched larvae may then enter the lower part of the digestive tract.…”

“…3,17 The demographics of patients were diverse: the sex ratio was even (52% of cases involved women), and the median age was 36 years, including both infants and elderly (1-64 years). The distribution was wide, from tropical areas 15,16 to semi-arid regions, 18,19 and zones with temperate climates. 4,20 Most cases have been reported in developing countries where sanitary conditions are poor, especially in rural environments, with the exception of a handful of cases in urban areas.…”

“…4,20 Most cases have been reported in developing countries where sanitary conditions are poor, especially in rural environments, with the exception of a handful of cases in urban areas. 15,18,19,21 Unfortunately, the source of contamination has been rarely described with precision. A few infestations have been related to the consumption of stagnant water from a garden fountain 8 or water extracted from uncontrolled domestic supply systems that actually showed defects.…”

“…4,17,22 Besides, a few cases may have been the result of the consumption of contaminated foodstuffs, 23,24 such as French watercress 14 or mangos. 15 Empirical antiparasitic treatments, such as metronidazole 19,41 or co-trimoxazole, 8 have been prescribed in some cases. However, there is no validated proof of their efficacy, and their usage therefore remains disputable.…”