Kingdom Animalia Class Insecta Family Calliphoridae Rank Species | Phylum Arthropoda Order Diptera Tribe Calliphorini | |
Similar Gyrostigma, Cordylobia, Cobboldia, Gasterophilus, Wohlfahrtia | ||
Cordylobia rodhaini also known as the Lund's fly derived its common name from captain Lund, who was the first European to show symptoms of the disease caused by the larvae of the same fly. The Lund’s fly belongs to the genus Cordylobia, a group of flies from the family Calliphoridae. The currently known species comprising the genus Cordylobia include: C. anthropophaga, C. ebadiana, C. praegrandis, C. rodhaini and C. ruandae. The larvae of the Lund’s fly are parasites of thinned-skinned mammals, especially the Gambian rat, mona monkey and small antelopes and are only accidental parasites of humans. The adult flies feeds on rotting fruits, vegetables and animal feces, and are most abundant in the wet season. Like many tropical insects they are most active in the dark periods and have the greatest activity early in the morning and late in the evening while resting typically between 8am to 5pm. The Lund’s fly are largely confined to tropical Africa, especially the rainforest areas in Sub-Saharan Africa. However, as a result of human migration, the parasitic infections they cause have been recorded in other continents including Europe and Asia.
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Life Cycle
The life cycle of the Lund's fly, typically lasts from 55 to 67 days. The female fly lays up to 500 eggs and deposits her eggs on dry sand polluted with the excrement of animals, or can also lay them on damp human clothing. In about three days, the larva attached to its host, is then activated by the warm body of the host. The Lund’s fly larvae then hatches and breaks through the skin. A maturing larva induces a painful swelling. In approximately 12 to 15 days, the larva reaches a length of about 23 mm, exits the skin of the host, and falls to the ground to pupate. The adult fly emerges in 23 to 26 days, and the life cycle continues.
Larvae structure
The Lund’s fly is parasitic at its larval stage. Under examination with a scanning electron microscope, it appears whitish and barrel-shaped, with 11 segments. Its body is almost completely covered by large conic-shaped spines. These spines serve as a point of attachment to its host. The larvae have a brown apex, pointing towards the posterior end where there are fewer spines. There exist two bulges in the anterior end with paired mouth hooks at the anterior end of the larvae. After hatching, the larvae penetrates into the dermis and molts to second and third instar larvae before emerging from the skin. The third instar larvae has an approximate length of 1.5 cm and is distinctively less elongated and conical in shape, compared to the second instar larvae
Lund's fly-induced myasis
Myasis is generally defined as the infestation of animal tissue by the larvae of some flies. The larva of myasis-causing flies feed on animal tissue and/or bodily fluids. Myasis caused by the Lund’s fly larvae have presently been reported in Ethiopia, Uganda, Congo, Kenya, Ghana and Cameroon. It is very similar to the myasis that caused by the Tumbu fly, the latter co-existing in the same geographical regions as the Lund's fly. Clinical symptoms start with the formation of a red papule, which is characterized by a small raised swollen area of the skin. These can form on any area of the skin, with the arms, legs, arms and back most frequently affected. Patients typically do not report pain at this stage of infection. The papule enlarges with time, penetrates deep into the skin and develops a central opening, now classified as a furuncle. The central opening facilitates gaseous exchange for the larvae while a serous fluid also exits the same opening. The central opening also makes it possible for the larvae to excrete its fecal matter. At this point, itching and burning sensation are usually described by patients in the affected areas of the skin. Patients also report symptoms such as insomnia (due to pains at night) and fatigue. The disease is usually self-limiting as the larvae drops out, upon reaching the third instar larval stage. Also there have not been any reports of Lund’s fly larvae infestation in systemic areas, such as the internal organs, or blood vessels. The most serious incident of Lund's fly induced myasis reported so far resulted in swelling of the lymph nodes due to adverse immune reactions in the patient. A major distinction between myasis caused by Lund’s fly and myasis caused by other flies is that lesions in Lund’s fly myasis are usually smaller and multiple. Myasis caused by Tumbu fly is, on the other hand, similar to that caused by Lund's fly which is mostly due to the fact that the two flies belong to the same family and might share similar characteristics as a result.
Treatment
As the larvae falls of eventually, the disease is self-limiting and no treatment is usually needed. However, to facilitate healing, the larvae can be physically removed from the infected region. This is done by applying gentle manual pressure to any two ends of the lesion until the larvae comes out Occasionally, petroleum jelly or oil is applied to the opening in the lesion, in order to prevent oxygen supply to the larvae, thereby forcing the larvae to move closer to the surface. Improper removal of the larvae could lead to inflammation of the lymph nodes as bursting of the fluid from the larvae could lead to allergic reactions in some people. Proper covering of the wound will prevent further infection. Unsterilized objects should not be used to open lesions as this could result in infection. Hyperpigmentation may persist on the skin of the infected area months after infection. Also lack of experience in diagnosing Lund's fly induced myasis could lead to a misdiagnosis of impetigo, insect bites, folliculitis or other skin disorders.
Prevention and control
Generally, humans are accidental hosts of myasis as a result of Lund’s fly larvae infestation and are therefore less likely to be infected. However, infestation can pose a health problem for the local population in the endemic region and tourists alike. Infestations of Lund’s fly larvae are usually diagnosed in tourists and foreign workers that previously travelled to the endemic regions. Therefore, incidence rates might be under-reported in endemic regions and might be treated by local means. Even as it can be spread by human travel, it has not reported to be contagious and is also less likely to thrive in regions other than Sub-Saharan Africa, due to differences in climate. As eggs are usually laid on wet clothing in endemic regions, clothes should not be left outside for long periods, specifically at dawn or twilight, as this is when Lund’s flies are most active and likely to lay eggs. Also, ironing all clothes to kill eggs or larvae will help to reduce the incidence of myasis. Good hygiene can also play a role in preventing myasis, as the Lund’s fly is known to feed in dirty surroundings and lay eggs where they breed.