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

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.

Risk of Attacks by Blackflies (Diptera: Simuliidae) and Occurrence of Severe Skin Symptoms in Bitten Patients along the Eastern Border of the European Union

“…As shown by our survey carried out in the southeastern part of Poland, blackfly bites induce solely skin lesions in as many as 88.52% of patients and both skin and systemic symptoms in only 11.48% [32]. The blackfly bite symptoms described previously were observed in patients with a good health status with no comorbidities.…”

“…Although many incidents of blackfly bites on humans and skin lesions caused by these insects have been reported worldwide [47][48][49][50][51][52][53][54][55][56][57], such cases have been monitored [58][59][60] and epidemiological studies have been conducted [61,62] in a few regions. In Poland, insufficient attention has been paid so far to the effects of the parasitism of blackflies on humans [32,63] despite the wide spread and mass occurrence of these insects in some regions [33,34,[63][64][65].…”

“…Many case reports described in the literature from the beginning of the 20th century (e.g., [67][68][69]) to the beginning of the 21st century [32,56,57,70] show highly diverse reactions in humans bitten by blackflies and, consequently, a wide spectrum of local and systemic symptoms. In addition to the individual traits and sensitivity of patients, the diversity of symptoms may also be associated with the biological and physiological features of these insects, probably the composition of the saliva of various species.…”

“…Forty-three patients (32 females and 11 males) with severe skin signs and systemic symptoms were selected from a group of patients reporting a blackfly bite incident in outpatient clinics of southeastern Poland. This group was excluded from the other studies conducted in the same period and described in our earlier report [32].…”

“…The survey consisted of two parts. The answers to the questions in the first part were presented in our earlier study [32]. In turn, the data on the circumstances of blackfly attacks on humans and the activity of the insects in the environment were used in this study.…”