Skin Lesions and Systemic Reactions in Humans Infested by Blackflies (Diptera: Simullidae) in Recreational Areas in Southeastern Poland.

Monika Sitarz,Weronika Buczek,Alicja Buczek

doi:10.3390/jcm10040788

Abstract

Due to their mass occurrence in some environments and high aggressiveness, blackflies (Simulium spp.) represent the most bothersome arthropods attacking humans. In this study, we describe the medical effects of blackfly infestations in humans in southeastern Poland. Local and systemic reactions to blackfly bites were monitored in 418 patients (61.24% of females and 38.76% of males) of medical centers. Only skin lesions at the site of the bites were found in 88.52% of the patients, whereas accompanying systemic reactions were diagnosed in 11.48%. The most common signs observed in the area of the bites were pruritus (94.74%), burning (55.02%), edema (44.02%), and erythema (40.91%). The skin lesions, which were most often grouped small papules and papular and purpuric lesions with a varied range, typically persisted for several days, or for several weeks in some patients. Statistical analyses confirmed that the persistence of the skin lesions did not depend on the sex of the patients and the number of blackfly infestations. The systemic reactions to the components of the blackfly saliva were manifested by headache, increased body temperature, arthralgia, lymphadenopathy, and menstrual disorders in the females. The patients were most often attacked simultaneously by many blackflies on exposed parts of the body, mainly the upper limb, lower limb, head, and neck areas. The investigations indicate that blackflies are an important etiological factor of dermatitis and other symptoms in humans; hence, they should be considered in clinical diagnosis.

Highlights

Substances contained in blackfly saliva and introduced by females during ingestion of blood from vertebrates cause simuliosis [18,19], which may exert the most dramatic effect, i.e., anaphylactic shock leading to death in humans [20,21] and animals [22,23,24]
We focused on the threats posed to human health by blackflies in southeastern Poland and on local signs and systemic reactions induced by the bites of these insects in humans
The massive occurrence of blackflies and their high aggressiveness towards hosts manifested by the substantial number of attacks of humans engaged in recreational and occupational activities suggest that, in some regions, blackflies should be regarded as an important causative factor of dermatitis, which may be accompanied by systemic reactions

Summary

Introduction

Blackflies (Diptera: Simuliidae) are arthropods with a worldwide distribution [1].Approximately 10–20% of species of over 2330 representatives of this family parasitize humans and animals, causing serious medical (e.g., [2,3,4,5,6]) and veterinary problems [7,8]and, large economic losses (e.g., [9,10,11,12]).Blackflies (Simulium spp.) occur most abundantly in areas located near fast-flowing rivers and streams, which are habitats for their pre-imaginary stages, i.e., larvae and pupae.Females of most species of these insects released from pupae obligatorily ingest blood of vertebrates, which is indispensable for their development and oviposition [13,14,15].Blackflies are important vectors of pathogens with considerable importance for public health, for instance, the best-known and widespread filarial worm Onchocerca volvulus, causing onchocerciasis (river blindness) in sub-Saharan Africa, some foci in Central andSouth America, and Yemen in the south of the Arabian Peninsula in Western Asia [16,17].Substances contained in blackfly saliva and introduced by females during ingestion of blood from vertebrates cause simuliosis (simuliotoxicosis) [18,19], which may exert the most dramatic effect, i.e., anaphylactic shock leading to death in humans [20,21] and animals [22,23,24]. 10–20% of species of over 2330 representatives of this family parasitize humans and animals, causing serious medical (e.g., [2,3,4,5,6]) and veterinary problems [7,8]. Females of most species of these insects released from pupae obligatorily ingest blood of vertebrates, which is indispensable for their development and oviposition [13,14,15]. Substances contained in blackfly saliva and introduced by females during ingestion of blood from vertebrates cause simuliosis (simuliotoxicosis) [18,19], which may exert the most dramatic effect, i.e., anaphylactic shock leading to death in humans [20,21] and animals [22,23,24]

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Discussion

Conclusion