
House fly is very common insect. Some insects are friendly to human society, while others are dangerous in transmitting human diseases. House fly is medically important. They belong with the Order Diptera, which means two winged flies.
House flies are 6-9 mm in length. Four stages in their life cycle are the egg, larva, pupa, and adult. In summer, the eggs generally hatch within 3 hours into larva. The average hatching time of egg is 48 hours. Larval period lasts up to 2 days, at the end of which larva transforms into pupa. Pupa stages lasts for 4 to 5 days in summer, but may be prolonged in winter. The adult emerges from pupa through a circular slit. Male and female mates within 24 hours after emergence from pupal case.

Owing to this habit, the fly can contaminate human food with the micro-organisms form the filth.

House flies can mechanically transmit bacterial infections such as Salmonella typhosa, S. paratyphi. S. enteritidis, Shigella dysenteriae complexa, Vibrio chlolerae, Mycobacterium tuberculosis, and M. leprae; viral diseases such as poliomyelitis, and infectious hepatitis. They also spread protozoan like Entamoeba histolytica, E. coli, and Giardia lamblia. The egg of Ancylostoma duodenale, Ascaris lumbricoides, and Echinococcus granulosus can be carried both internally and externally by this fly. The ova of helminths like Taenia solium, Enterobius vermicularis can be carried extrenally.
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