116 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



Life History and Pathogenesis. — The adults take no food. While 

 in flight, the fly will deposit larvae near the nostrils of sheep or other 

 animals suitable as hosts; the larvae then pass through the nasal cav- 

 ity into the ethmoidal, the frontal, or the maxillary sinus, where they 

 transform into the second instar. There the larval stage is completed, 

 and the mature larvae drop to the ground to pupate. The duration 

 of the immature stages varies considerably, but is more rapid in 

 warmer climates or seasons; the larval stage may be completed in 

 from 2y 2 to 12 months, or even in 25 days, and the pupal stage in 3 

 to 4 weeks. In Europe there is supposedly one annual generation, 

 although evidence points to two in North America. 



Though not a normal host, man is often infested, especially when 

 he is closely associated with sheep or goats. Apparently he may be 

 infested at any time during the summer or early fall. Numerous cases 

 of myiasis in man are on record, and it is probable that the infestation 

 is even more common than the literature would indicate. Several 

 cases are from the United States ; in some parts of Russia, Italy, North 

 Africa, and on the Cape Verde Islands it is a common affliction. 



In human beings this parasite usually affects the conjunctiva of the 

 eye, to produce a painful, but usually not serious, form of conjunctivi- 

 tis. The larva can never progress beyond the first stage. In the typi- 

 cal case history the patient will report being struck in the eye by an 

 insect or small foreign object, with pain and inflammation developing 

 a few hours later. The larva, because of its small size and transpar- 

 ency, is hard to see, and the cause of the conjunctivitis may easily be 

 missed. As many as 50 larvae have been removed from the conjunc- 

 tival sac of a single patient, although usually the number is much less. 

 Cases of ocular myiasis caused by this parasite resemble cases of acute 

 catarrhal conjunctivitis, and may be diagnosed as such. Since the 

 parasite cannot develop, the trouble usually lasts but a few days. 



In Algeria native f shepherds are subject to the attacks of the sheep 

 bot, which sprays its larvae into the eyes, nose, and throat. Attacks 

 occur chiefly where the sheep population is sparse as compared with 

 the human population. The flies may be attracted by the odor of 

 cheese which the natives eat. Similar cases have been reported from 

 Italy and from the Cape Verde Islands. In oral and nasal myiasis, 

 known as thim'ni in Algeria and as tamne in the Ahaggar Mountains 

 of the central Sahara, the parasite penetrates the nasal cavities and 

 frontal sinuses, where it may cause swelling and severe pain, with 

 frontal headaches that make sleep impossible, or enters the mouth 

 causing inflammation of the throat which makes swallowing difficult. 

 The symptoms may last from 3 to 10 days, or longer in the case of in- 

 flammation of the nose. 



This species has also been reported to be involved in myiasis of the 

 ear, the larva attacking the membrane of the outer auditory meatus 

 and causing considerable pain, although not penetrating the tym- 

 panum. 



Literature. — Portchinsky's {116) monograph gives the most com- 

 plete account of this parasite in relation to man. For a discussion of 

 the first larval stage in comparison with that of Rhinoestrus pur- 

 pureas, see Larrousse (80), and for the other larval, pupal, and adult 

 stages and the biology, see Rodham and Bequaert (123). For some 

 complete case histories, symptomology, and diagnosis, see Dupuy 

 d'Uby (37). te l y 



