House Flies - House of Pathogens - Report Example

House flies: House of pathogens Kingdom: Animalia Phylum: Arthropoda Insecta Order: Diptera Family: Muscidae Genus: Musca Species: M.domesticaBinomial name: Musca domestica Linnaeus,1758 Common name: House fly Introduction The Musca domestica Linnaeus commonly know as ‘House fly’ is a filth, true fly with two wings. They are well known nuisance pests vectoring various pathogens like viruses, bacteria, fungi, protozoan and nematodes posing serious health disorders both to animal and mankind. Evolution and Distribution The house fly belonging to large filth fliers group are strong fliers believed to have evolved in the beginning of Cenozoic era, originated in Steppes of central Asia. Due to its association with human and human activities today it is cosmopolitan in nature seemed to have spread along with the migration of man. It survives in all the continents ranging from tropical to temperate environments. Habit House flies survive only in the human environment flourishing well on the same kind of food and temperatures as that of man, breeds and reproduces in manure, exposed human faeces, dungs heaps and all kinds of filths. Hence it is be attributed as an important filth fly. This nature attributes them to be good scavengers. The houseflies are active only during the day and rest at night feeding on anything and everything. It usually prefers liquids but in case of solids it deposits saliva on food to dissolve it, then sucks, and regurgitates. The feet of the flies contains taste buds and smell receptors. Their food intake is very high consequently egestion being constant. This factor names the insect to be very dangerous and heinous carrier of pathogens. Life cycle Figure 1 Diagrammatic representation of life cycle of the house fly. The life cycle of the house fly is an excellent example of complete metamorphosis and sex determination mechanism. House flies release a pheromone called “muscalure” the function of which is both aggregation and sexual attraction. They feed well before copulation and copulate within 2 minutes or it may last as long 15 minutes. Ovipoistion starts 4 to 20 days after copulation. Normally females mate only once in their life time and store the sperms to use it repeatedly to lay eggs in several sets. Each female can lay up to 9,000 eggs and can fly up to one or two miles in search of favorable egg laying places. The life cycle consists of egg, larval/maggot, pupa and adult stages and takes about 7 to 10 days under warmer climatic conditions and under suboptimal conditions around two months. The house flies exhibit different sex determination mechanisms such as male heterogamy, female heterogamy and also maternal control over sex determination of the offspring. Also a very important feature of Houseflies is their rapid fluctuations in population density where they populate about twice their existing density in a few days (Imai 1984). These population outbreaks pose a major threat as high density populations have greater nuisance value and always cause outbreaks of various diseases. Stage I: Egg The eggs are white in color about 1.2mm in length laid singly and piled into small groups consisting of about 75 to 150 eggs. The important criteria for the eggs to hatch are moisture of the manure without which they fail to hatch. The eggs hatch into legless maggots within 8 to 20 hours, feed on the immediate nutrient rich substrate and begin further development. Stage II: Larva Early instar larvae are creamy to whitish in color, cylindrical in shape with tapering head, measuring about 3 to 9mm long. The larva under goes three instar stages and develops into fully grown maggot of about 7 to 12mm long, creamy in color and with greasy appearance. Temperature of about 17 to 35⁰C and moisture rich nutrient substrates favors larval growth to maximum. Fully developed maggots crawl to drier, cooler region and transform into pupal stage. III stage: Pupa The last larval skin of the maggots forms pupal case. The pupa is about 8 mm long, round at both ends blunt in shape and varies in color from yellow, red, brown to black in color as the pupa ages. At about 32 to 37⁰C the pupa develop into adult flies in about 2 to 6 days where as at about 14⁰C they take 17 to 27 days. The mature fly escapes from the pupal case from the sac called ptilinum present on the head. Figure 2 Larval stages of house fly (courtesy: http://entomology.unl.edu/)1 IV stage: Adult Figure 3 Adult House fly (courtesy: http://entomology.unl.edu/)1 Adult house fly is relatively small, soft bodied with large eyes, dull grey in color with four dark stripes on the thorax of the body. Females are usually larger than males and can be distinguished by the presence of the relatively wide space between the eyes. The life span of adults is about 15 to 25 days but may also live up to 2 months. After emerging from the pupae, its growth is complete and the flies cease to grow further. However availability of food and cooler temperatures favor its longevity. Vector of diseases Though house fly does not bite, its entire body swarms with many pathogens picked from the feeding and breeding grounds. House flies not only mechanically transmit pathogens existing on their body but also their mouthparts and digestive systems harbor few pathogens for several days and are later transmitted when the fly regurgitates the contents of the stomach onto food to liquefy before ingesting or defecate, thus contaminating the food and food preparation surfaces. Diseases in humans House flies mechanically transmit various diseases. Food poisoning and diarrhea are common symptoms of many infections. It also transmits eggs of helminthes e.g., Ascaris Lumbricoides, Trichuros Trichura, Haemenolypes nana, Enterobius Vermicularis. It is also causal agent for accidental myiasis, poliomyelitis, tuberculosis and infective hepatitis. Campylobacteriosis is an infectious disease caused Campylobacter. Most people who become ill with campylobacteriosis get diarrhea, cramping, abdominal pain, and fever within 2 to 5 days after exposure to the organism. Escherichia coli (abbreviated as E. coli) are a large and diverse group of bacteria. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness and pneumonia, and other illnesses. The enterococci frequently causes nosocomial infections, particularly in intensive care units of hospitals. Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. Salmonellosis is an infection caused by Salmonella. Most persons infected with Salmonella develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. Shigellosis is caused by Shigella. Most who are infected with Shigella develop diarrhea, fever, and stomach cramps starting a day or two after they are exposed to the bacteria. Chlamydia is a common sexually transmitted disease caused by Chlamydia trachomatis, which can damage a womans reproductive organs. Even though symptoms of chlamydia are usually mild or absent, serious complications that cause irreversible damage, including infertility, sets in even before it is diagnosed. In infected males Chlamydia cause discharge from the penis. Eberthella typhosa causes typhoid fever which is a life-threatening illness where about 21.5 million people every year are affected in the developing countries. It is also known to transmit porcine transmissible gastroenteritis virus (TGE). Diseases in animals: Flies spread diseases in animals also. Myiasis: is an condition infected with maggots of the fly. This condition is very common in cattle (Hall and Smith, 1993 ). The house fly carry Chlamydia trachomatis the causative agent which causes opthalmia in cattle. It is the vector of cestodosis in poultry. It is also known to spread coccidiosis in poultry. Apart from transmitting diseases house flies also induce economic problems like reduction in milk production as cows expend extra energy fending off flies, Increases the frequency of animal diseases leading to more medication costs and veterinary services. In poultry farms the manure below the caged hens is potential breeding sites for flies resulting in transmission of above mentioned diseases. Tolerance House fly tolerance depends on the environments where they are present. Sensitive places like Hospitals, restaurants, food preparation and packaging units and dairy/dairy products packing units have zero tolerance towards this fly. In slaughter homes, livestock or poultry farms control of these flies are inevitable. Control and management The role of flies as potential vectors for various pathogens and/or with a minor role for transmission of few causing various diseases is well established. Hence adequate measures to ensure control of these flies from epidemiological point of view are justified. The effective and efficient control measures can be listed as follows; Sanitation: The basic and more economical step in the management of fly is good and improved sanitation. This is more practical way to primarily eliminate the breeding sites of the flies. Decaying organic matter, filth, animal faeces or mortalities should be immediately cleared. In dairy fields the manure should be cleaned regularly and animal areas should be kept dry as much as possible. Wet straw should not be used as bedding material and spilled feed should be avoided and cleaned. Waste disposal: organic and food left overs should be disposed off immediately to prevent from being breeding and feeding sites for the flies. The dumpsters should have tight lids and should be thoroughly cleaned to avoid it from being the breeding grounds. Food should not be under exposed conditions. In kitchens and food serving places the spills should be cleaned immediately. Food eating places and surfaces can be cleaned with disinfectants. In hospitals and also home, floors and toilets should be cleaned with disinfectants and if possible with fly repellants. Use of Plain boiling water effectively kills maggots in rubbish bins and other places. Exclusion: Flies can be excluded from the house hold premises by using insect guard screens covering doors, windows and vents. Mechanically the flies can be trapped using i) Sticky fly paper ii) Ultraviolent light traps which can be used both in agricultural and non agricultural regions. The flies are attracted to the light of these traps and are electrocuted immediately on its contact. It is well suited in restaurants and other food serving regions. iii) Traps baited with sugar, fruit or meat, and also use of commercially available artificial pheromone (muscalure) is used in these fly traps. iv) Window fly traps are traps sticked on windows without insecticides. Chemical control though not advisable can be relied upon in integrated fly management program. Pesticide releasing fly strips can be used to attract filth flies. Contact non residual pesticides earmarked for fly control can be used to kill adult flies which provide temporary relief. Residual pesticides which remain active for some time can be applied to outdoor surfaces where the flies rest. Biological control Figure 4 House fly larvae fed by M.raptor larvae (courtesy: http://entomology.unl.edu/)1 Increased uses of insecticides have made flies exhibit cross and multiple resistance to these chemicals also imposing health risks to humans (Chapman & MacNicoll 2002). Hence an alternative method involving natural means is appreciated. Chalcidoid wasps belonging to pteromalidea, Muscidfurax and Sphalangia spp.Ichneumonids and other parasitoids are predators of house flies. M.raptor and S.cameroni wasps are very useful in poultry farms (Fig.3 ). The wasp larvae feed on house fly larvae thus employing control before birth. Certain predatory mites and beetles found the older manure also feed on housefly eggs and maggots. References 1. Hall, and Smith, “Diptera causing myiasis in man”. Medical Insects and Arachnids (eds R.P. Lane & R.W. Crosskey), Chapman & Hall, London, UK. (1993): 403–428. 2. Imai, C. “Population dynamics of houseflies Musca domestica on experimentally accumulated refuse. ” Researches on Population Ecology (Kyoto), 26(1984): 353–362. 3. Learmount, Chapman, and MacNicoll, “Impact of an insecticide resistance strategy for house fly (Diptera: Muscidae) control in intensive animal units in the United Kingdom”. Journal of Economic Entomology 95 (2002): 1245–1250. 4. 1http://entomology.unl.edu Read More