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Paederus dermatitis In Sierra Leone

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Paederus dermatitis In Sierra Leone
Syed Nurul Rasool Qadir MMBS1, Naeem Raza MMBS2, Simeen Ber Rahman MD3
Dermatology Online Journal 12 (7): 9

1. Combined Military Hospital, Kharian, Pakistan. s_qadir2004@hotmail.com2. Combined Military Hospital, Abbottabad, Pakistan 3. Military Hospital, Rawalpindi, Pakistan


Paederus dermatitis, a type of irritant contact dermatitis attributed to a Staphylinid beetle, is prevalent in most parts of the world. We studied 50 cases of Paederus dermatitis at the United Nations Hospital at Koidu Sierra Leone (West Africa), over a period of 6 months from Oct 2003 to Mar 2004. The objectives of the study were to determine clinical patterns of dermatitis and its response to topical steroids, with and without antibiotics. Patients with a definite history of contact with the insect were included in the study. Amongst these, 14 of the more severe cases were treated with oral prednisolone or intralesional triamcinolone acetonide. The remainder of the 36 patients were divided in two equal groups A and B. Patients in Group A were treated with topical diflucortolone valerate 0.001 percent and oral cetirizine hydrochloride; patients in group B were given oral ciprofloxacin in addition. In 50 patients studied, 43 (86 %) were males and 7 (14 %) were females. The neck was the most common site involved followed by face. Healing time ranged from 14 to 28 days and lesions in all the patients healed with residual dyschromia. Healing time was shorter in Group B patients in comparison with those in Group A. Paederus dermatitis in Sierra Leone is a relatively severe form of this dermatitis. The better response to a combination of topical steroids and oral antibiotics may indicate concurrent bacterial infection.


Irritant contact reactions are inflammatory responses of the skin to exogenous agents, in which inflammatory mediators may be activated but memory T-cell function or antigen-specific immunoglobulins are not involved. The main pathophysiological changes observed in irritant contact dermatitis are skin-barrier disruption, epidermal cellular changes, and cytokine release mainly from keratinocytes [1]. Irritants produce various responses on the skin that range from stinging, burning, and tightness to erythema, urticarial reactions, frank eczema, or chemical burns. The same chemical may produce different responses depending upon its concentration, duration of exposure, and individual responses. Although the nature, concentration and duration of contact with a chemical are of primary importance, mechanical, thermal, climatic, and constitutional factors play an important role in many irritant reactions [2].

Figure 1 Figure 1b
Paederus sabaeus Erichson (Rove beetle, Champion fly, Nairobi fly)

Paederus sabaeus Erichson also known as the Nairobi fly or Champion fly [3] is a Staphylinid beetle found in both East and West Africa. The genus Paederus has almost 600 species worldwide. It belongs to the order Coleoptera, family Polyphaga and sub-families Staphylinoidea, Staphylinidae and Paedrinae. It is an active predator of several crop-damaging insects and occurs in warm tropical climates [4]. The insect (Fig. 1) breeds in wet rotting leaves and soil. The population increases rapidly at the end of the rainy season (November and December) and then rapidly diminishes with the onset of dry weather in January. A rapid increase in their population has been attributed to the increased rains associated with the el Niño phenomenon [5]. Paederus dermatitis (also known as night burn) is the irritant contact dermatitis associated with contact with Paederus spp. (Fig. 2) ; the beetle is drawn to light fixtures and candles at night [6]. The beetle does not bite or sting, but when crushed against the skin it releases a potent toxin known as pederin that results in itching, burning, erythema and oozing 12-48 hours later [7]. Biosynthesis of pederin occurs in only certain female rove beetles. The female beetles producing the toxin are designated as (+) female rove beetles and those lacking these biosynthetic capabilities are aposymbionts and designated as (-) females [8]. Certain endosymbiotic gram-negative bacteria are probably essential for the synthesis of pederin and are present only in the (+) females. The DNA of the symbiotic bacteria belongs to the gamma subdivision of the proteobacteria that are clustered within the genus Pseudomonas, and closely related to Pseudomonas aeruginosa [9, 10]. Because of its irritant nature, pederin extract is also used as a self-medication for treatment of vitiligo in some parts of the world. Severe chemical-burn-like lesions have occurred after the application of crushed pederin extract on vitiliginous skin [11].

Conjunctivitis can occur from contact with eyes and is also known as Nairobi eye in Africa [12]. The mucosal surfaces are relatively less affected by the toxin than the skin [13]. Skin lesions are usually linear, vesico-bullous, or pustular on an erythematous base [14]. Systemic IgE mediated hypersensitivity reactions are exceptionally rare [15].

The objectives of the study were to note clinical patterns of Paederus dermatitis and its response to topical steroids, with and without oral antibiotics.

Material and methods

This observational and experimental study, conducted over a period of 6 months from October 2003 to March 2004, involved 50 patients at the United Nations Level-II hospital in Koidu Sierra Leone. The patients included military personnel, civilian workers of the United Nations and various non-governmental organizations (belonging to various nationalities), and members of the local population. Patient ages ranged from 22 to 42 years. They included both sexes and all races.

Only those patients with a definite history of contact with the insect were included in the study. They either presented with itching or burning sensations over skin lesions, or in some cases were totally asymptomatic with the skin signs as the only presenting feature. Children, the elderly, and patients with a doubtful history of contact with the beetle or other plausible causes of contact dermatitis were not included in the study. Patients with a previous history of chronic skin disease or allergy were also excluded.

All patients were subjected to a detailed history, including personal history of skin diseases, atopy or allergies, and family history of skin diseases. Thorough dermatological and systemic clinical examinations were carried out. Treatment was then initiated and all patients were examined weekly until complete healing occurred. Weekly followup examinations were conducted for 2 months subsequently.

Out of the 50 patients, 14 were severe enough to require treatment with intra-lesional or oral corticosteroids. These patients had diffuse desquamation or marked epidermal necrosis and were treated either with intralesional triamcinolone acetonide (diluted to 10mg/ml—Kenacort A® injection, Squibb) or oral prednisolone (30 mg once daily for 7 days—Deltacortil®, Pfizer).

The remaining less-severe 36 cases were randomly divided into two groups. Group A was treated with twice daily topical diflucortolone valerate (0.001 %, Nerisone®, Schering) along with once daily oral cetirizine hydrochloride (10 mg Zyrtec®, UCB). Group B was treated with twice daily ciprofloxacin (500mg Ciproxin®, Bayer) in addition to topical diflucortolone valerate and oral cetirizine hydrochloride.

The clinical data was subjected to statistical analysis using the statistica program for the social sciences (SPSS version 10) computer program. The p-value was determined using the chi-square test and p value of less than 0.05 was considered significant.


Figure 2 Figure 3
Figure 2. Paederus dermatitis
Figure 3. Involvement of the neck, the most common site

Of the 50 patients studied, 43 patients (86 %) were males and 7 patients (14 %) were females. The ages of the patients ranged from 22 to 42 years with a mean of 26.22±6.51. No significant difference was observed in either the clinical features or therapeutic outcome on the basis of gender, race, or nationality.

Of the 50 patients, 40 patients (80 %) were symptomatic with sensations of itching or burning, the burning sensation was more pronounced compared to itching. None of the patients complained of pain. There were 10 (20 %) patients who were asymptomatic and presented with skin lesions only.

Clinically all the patients had intact or ruptured vesicles (erosions) on an erythematous base. Large bullae were present in eight patients (16 %). A striking feature was the presence of numerous micropustules interspersed with the primary vesicular lesions in 43 patients (86 %). Unfortunately, because of the lack of facilities, microscopy or culture from these lesions could not be performed. Marked epidermal necrosis or diffuse desquamation was seen in 14 patients (28 %). All our patients exhibited residual dyschromia after healing (80 % hypopigmentation, 20 % hyperpigmentation). Scarring was not a feature in any patient.

The most commonly involved sites were the neck (Fig. 3) and the face (see Table I). A periorbital predilection was present in 75 percent of the facial lesions.

More than one lesion was present in 38 patients (76 %); there were 26 patients (68.42 %) with two lesions, 11 patients (28.94 %) with three lesions, and 1 patient (2.63 %) with four skin lesions. No kissing lesions were seen.

The healing time in majority of the patients (78 %) was 2-3 weeks. None of the lesions healed in less than 7 days; in 11 patients (22 %), the healing took 28 days. Out of 36 patients having less severe lesions, healing time was less in Group B patients than in Group A patients (see Table II). This observation was statistically significant (p <0.001).


Paederus dermatitis occurs predominantly on exposed parts of the body [6, 16, 17]. Face and neck were found to be the most commonly involved sites in an Iranian study reported by Zargari et al. [18] as well as a Pakistani study conducted by Kakakhel [17]. Our study also found the dermatitis more commonly over uncovered parts of the body; the majority of the lesions were on the neck and face. Facial lesions had predilection for the periorbital region in 75 percent of our patients. Zargari et al. reported also multiple lesions in 75 percent of cases, which is comparable to the 76 percent of patients in our study. However they reported that 5 percent had kissing lesions, which were not found in any of our patients. They also described diffuse desquamation and epidermal necrosis in only 15 percent of cases, whereas 28 percent of our patients had a severe reaction. The severity of the reaction probably is attributable to a more potent toxin produced by the local species of Paederus sabaeus Erichson compared with the Iranian species Paederus ilsac Bernhaurt and Paederus iliensis Coiffait [18]. Potency of the toxin in our study is also indicated by the presence of large bullae in 16 percent of the patients, which is a rarely reported finding in Paederus dermatitis. In a study conducted by Couppie et al. in 1992 [19], the uncomplicated lesions of Paederus dermatitis healed within 7-10 days, whereas healing time in our patients ranged from 14 to 28 days with majority of the lesions healing in 14-21 days. This finding can also be explained on the basis of more severe reaction to more potent toxin produced by the local species of Paederus sabaeus. Mokhtar et al. [20] reported only 17 percent residual effects compared to the 100 percent dyschromic changes found in our patients, again implying severe involvement of epidermis in our patients. Dursteler et al. also found gradual resolution of the lesions with residual areas of hypo- and hyper-pigmentation in the patients deployed in Pakistan [21].

The better response to oral antibiotics in combination with topical steroids in our patients suggests a concurrent bacterial infection; most of the Paederus spp. harbor symbiotic gram-negative bacteria [9] that probably contaminate the area when the beetle is crushed against the skin. Further studies need to be carried out to find out the role of bacteria in complicating Paederus dermatitis.


Paederus dermatitis, associated with Paederus sabaeus in Sierra Leone, is relatively more severe compared to Paederus dermatitis occurring in other regions, as indicated by lesions with diffuse desquamation, marked epidermal necrosis, large bullous eruptions, residual dyschromia, and a longer healing time. The better response to oral antibiotics in combination with topical steroids and oral antihistamine in our patients, in comparison with the use of topical steroids and oral antihistamine without the addition of an oral antibiotic, suggests the presence of concurrent bacterial infection; most of the Paederus species harbor symbiotic gram-negative bacteria that may contaminate the area when the insect is crushed against the skin.


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