The second case of cutaneous myiasis caused by Cordylobia anthropophaga (Tumbu fly) in Sri Lanka

Invasion of living tissue by the larvae of certain species of the Order Diptera which comprises in­ sects whose adults possess one pair of wings and a pair of halteres is called myiasis. The larvae of certain species of flies belonging to the genera Dermatobia, Callitroga, Chrysomyia and Cordylobia of the above Order have been responsible for caus­ ing myiasis in the tropics. Cordylobia anthropophaga (Blanchard) which is commonly referred to in Af­ rica (where it is restricted to) as the "Tumbu fly" or the "Mango fly" or the "Skin maggot fly" is a non-metallic calliphorine with a vast area of distribu­ tion within the continent from Senegal and Ethiopia up in the North to Natal down in the South (1).


Introduction
Invasion of living tissue by the larvae of certain species of the Order Diptera which comprises in sects whose adults possess one pair of wings and a pair of halteres is called myiasis. The larvae of certain species of flies belonging to the genera Dermatobia, Callitroga, Chrysomyia and Cordylobia of the above Order have been responsible for caus ing myiasis in the tropics. Cordylobia anthropophaga (Blanchard) which is commonly referred to in Af rica (where it is restricted to) as the "Tumbu fly" or the "Mango fly" or the "Skin maggot fly" is a non-metallic calliphorine with a vast area of distribu tion within the continent from Senegal and Ethiopia up in the North to Natal down in the South (1).
To date, there have been only five cases of human myiasis reported from Sri Lanka. Three of these due to Chrysomyia bezziana were indigenously ac quired and the fourth due to C. anthropophaga was acquired following a visit to Africa. The first re port is about two cases of myiasis of the nose and the ears due to C. bezziana secondary to chronic suppurative sinusitis and chronic otitis media re spectively (2). The third case of wound myiasis due to C. bezziana has been reported from a chronic ulcer in the right foot of a 70 year old female (3). A case of myiasis on the scalp of a 10 month old infant who had previously been in Zimbabwe with his Sri Lankan parents has been attributed to C. anthropophaga which is not found in Sri Lanka (4). The 5 ,h case is that of a 28 year old German national who had acquired myiasis of the scalp due to the larvae of Dermatobia hominis while on tour in Sri Lanka (5).

Case Report
Here we describe the second imported case of cutaneous myiasis due to C. anthropophaga in a Sri Lankan adult male following a 2-week visit to Cameroon, Africa. The patient is a 46 year old fac tory mechanic who had gone to Cameroon to undergo a short course of training related to his work. Two days before leaving Cameroon he had noticed a slightly tender, reddish-pink papule about 6 cm below and 1.5 cm medial to the right acromioclavicular joint in the skin of his anterior chest (Fig. 1). During the first three days there had been a slight, localized pain but no itching or fe ver. Ten days after he had first noticed the lesion, a live whitish maggot had popped out on squeez ing the lesion.

Description of the larva
The larva is a creamy white maggot (Fig. 2), mea suring 13mm, in length and 7 mm, in width hav ing a sluggish movement. The body is broadly oval, cone shaped consisting of twelve clearly marked segments covered with backwardly di rected curved spines.

Fig. 2: Maggot (3 rd instar larva) of "Tumbu fly", Bar = 10mm
The cephaloskeleton was dissected and this and the posterior spiracles were mounted in Depex after standard fixing, dehydration and clearing procedures. The labial sclerites of the cephalos keleton are long and curved (Fig. 3). The peritreme of the posterior spiracles is only faintly sclerotised and the slits slightly sinuous giving it a question mark (?) appearance while the button is indistinct. The larva was identified as a 3 rd instar larva of C. anthropophaga.

Discussion
The labial sclerites of the cephaloskeleton of the maggot are long and curved which feature dif ferentiates the 3 rd instar larva of C. anthropophaga from those of other species of the genus (6). The structure of the posterior spiracles with the indis tinct peritreme and button and the somewhat sinuous slit is typical of the species.
The female fly lays eggs in urine or faeces con taminated with dry sand or soil and also on dirty linen or clothes when hung out to dry. The larva hatches out after one to three days and remains attached to the surface. On coming into contact with a host it penetrates the skin, enters the der mis and remains there until mature.
Cameroon where the patient had stayed is a coun try situated within the area inhabited by C. anthropophaga. He stated that when clothes were hung out to dry, swarms of flies were found rest ing on them. It is likely that he got the infection from these clothes.
Though many 1st instar larvae may enter and es tablish themselves in the skin of the host all do not undergo development to reach maturity, there being a vast difference between the number of larvae reaching maturity and the 1st instar larvae entering the skin. This may partly be due to the innate resistance of the host to the infection and might probably explain why even though :he clothes hung out were teeming with flies only a single maggot was able to establish itself in the patient's skin. Some degree of immunity due to the previous infection is said to be acquired by humans as well as animals. In man this may not last longer than a year (6).
Penetration of the 1st instar larva hardly causes any irritation but in some cases significant skin reactions do occur. During the 1st two days a slight pricking pain may at times be experienced. The furuncle grows in size but the itching stops for a few days and recurs later with the pain in terfering with sleep. Exudation of serous fluid may take place with the tissue round the boil be coming indurated and red in colour.

Second case of myiasis caused by Cordylobia anthropophaga
In this case there was only one larva but if sev eral larvae are present and if adults of both sexes are released from these, there is a chance for the fly to breed and multiply. Since there is a wide variety of indigenous potential hosts such as ro dents and the climatic conditions are conducive for the fly, the possibility of the infection getting established in this country is a matter of concern especially because of increased travel between Africa and Sri Lanka today due to employment opportunities and tourism. Steps should be taken to monitor these imported infections as these could be potential health hazards.