Arthropods are probably the most successful of all animals. They are found in every type of habitat and in all regions of the world. They feed on a wide variety of plant or animal material and have been known as major causes of disease for centuries.

Without the vector, the parasite life cycle would be broken and the pathogen would die. Vectors can cause harm in different ways. They may cause illness on places, and this may happen through the consumption of food contains human enteropathogens, mechanically transmitted by flies or cockroaches. Muscoid dipterous insects have always been associated with human and domestic animals due to the abundance of food resources found in stables and domestic garbage. These flies are of major concern for veterinary medicine due to their capacity to act as a vector of several pathogenic organisms such as protozoa cysts, helminth parasites, enteropathogenic bacteria, and enterovirus (1).

Stored food products may be damaged or contaminated by live or dead insects, faeces, odours, webbing or cast skins. Furthermore, vectors such as mosquitoes may be introduced, and established in areas in which they have not previously been found (2), and where vector borne diseases can spread. Closed living accommodation favour the spread of ecto-parasites from person to another. Overcrowding, bad hygiene and lack of ventilation made the place an ideal environment for infection.

Soil transmitted helminths (STH) are relatively common parasites in the slum and rural area of many countries (3,4), this high prevalence of which is closely related to poverty, poor environmental hygiene, and impoverished health services (5). The main source of transmission is defecation outside latrines by heavily infected persons (6). While contaminated water, carrier, and food handlers might be the major transmission mode, indirect transmission by non biting flies can not be excluded (7, 8). Many authors have indicated that the primary school children are an ideal target group for (STH) (9), as they frequently defecate indiscriminately around their houses, particularly in the courtyards, sitting room, drains, even where every house hold has s latrine (10,11).

Over 50 species of synanthropic flies have been reported to be associated with unsanitary conditions and involved in dissemination of human pathogens in the environment (12).

In unsanitary communities, garbage, dead animal carcasses, and piles of faeces, are often scattered around the houses. Flies are commonly found both indoor and outdoors. They persist on excrement, dead animal bodies, and contaminated areas where faecal matter, large amounts of organic waste, and piles of garbage are left exposed an unattended (13), theoretically, flies can transmit helminths through mechanical or biological means (14). The effectiveness of faeces in enhancing the transmission of infectious agent by house flies is much greater than of any other substrate or medium. This is a result of faecal viscosity, which increases the efficiency of tarsi and bristles in tapering particles suspended in the faeces (15). Human pathogens can also be transmitted as airborne particles for short distances from fly-electrocuting traps, as electrocuting traps do not alter the infectivity of pathogens transported by flies (16). There are size limitations regarding the transmittal from the communicated sites. Bigger particles such as helminth eggs are transported by flies on their external surface, i.e., exoskeletons, while small cystic stages of human infectious intestinal protozoa can be ingested as well as transported on the exoskeleton.

When infected persons excrete in open areas, there is an increased risk of contact between flies and pathogen-positive faecal matter (17). Several studies have shown that eggs of Ascaris lumbericoides, Trichuris trichiura, hook worm, Entrobious vermicularis, Taenis sp., Hymenolips nana, Toxocara canis, hook worm larvae, and Strongyloides larvae are carried by many species of house flies (17, 18).

Cockroaches are among the most notorious pests of premises, they frequently feed on human faeces, and therefore they can disseminate cysts of enteric protozoans in the environment if such faeces are contaminated (19). They not only contaminate food by leaving droppings and bacteria that can cause food poisoning (20) but also they transmit bacteria, fungi, and other pathogenic microorganisms in infected areas (21, 22). Cockroaches feed indiscriminately on garbage and sewage and so have copious opportunity to disseminate human pathogen (23, 24). Also their nocturnal and filthy habits make them ideal carriers of various pathogenic microorganisms (25). Some parasites have been found in external surface or internal parts of body of cockroaches and some study have shown that exposure to cockroach antigens may play an important role in asthma-related health problems (26,27).

The study was carried out in an unsanitary community where parasitic infections and soil contamination with helminth ova were high and where flies were abundant in defecation area and house hold environment.

The ethics committee for this study protocol has approval from the governorate.

Material and method

Study area:

The study area was Khalidyia village. It is located north of the Fayoum city.  The village complain severe lack of services, although it occupies a unique tourist site that is far less than half a kilometer from Qarun lake.

This area was chosen because when we conducted a study of parasite infections in affected area, many piles of faecal matter were observed in the nearby swamp of the study.

Numerous flies were feeding on the extract and many were resting on plants near the extraction near the swamp that was an area for making dried cuttle-fish. During the process, a lot of flies fed and rested on the cuttle-fish. A community of poorly constructed domiciles resided near the swamp, crowded together in an unhygienic environment, with dirty houses, floors, scattered garbage and damp soil around the houses. Flies were seen everywhere in the area on food during meals, around children eating confectionery, sleeping children, dropped food, baby toys, and garbage. The abundant of flies around the house hold was attributable to the stock of rotten fish, and by product of the cuttle-fish harvest.

Flies collecting:

Flies were collected from the swamp and the nearby community, since many flies were seen on every pile of faecal matter in the swamp. The best method for collecting them was by stool bait trap.

FIELD-EXPEDIENT BOTTLE TRAPS

Fly traps can be fashioned from disposable plastic water bottles.  The simplest of these is constructed by cutting off the top and inverting it to form a cone leading into the body of the bottle, where bait is placed.  Flies attracted to the bait are trapped inside the bottle and disposed of when the bottle becomes too full to be effective (Figure 1).  Baits may consist of spoiling fruit or meat, food residue, and similar fragrant items.  Once flies are attracted into the bottle, their natural pheromones increase attractiveness of the trap to other flies.  These traps can be hung (no higher than 2.5-3 m) or placed on the ground out of traffic areas.

Under adverse environmental conditions, such as constant high wind, rain, or dust storms that prevent fly baits from being fully effective, it may become necessary to employ alternatives for dispensing baits. One such is to add poison bait to the trap illustrated above, or fashion a trap that is filled to a depth of 5 cm with poison fly bait and in which four 6 mm holes are cut near the top of the bottle to allow the flies access (Figure 2). The trap should be hung between 1 and 3 m above the ground.  These traps work well indoors.  The contents must be shaken periodically so that dead flies do not accumulate on the surface of the bait, inhibiting contact between newly attracted flies and the poison. Another technique is to place the bait in a box to keep it from blowing away or becoming soaked or dust-coated. Simply put granular fly bait in a flat box constructed from scrap wood, clearly labeled with the appropriate warning, and place the box on the ground where flies can access it. Such boxes should be checked periodically to dump dead flies and recharge them with bait. Dead flies should be disposed of with waste material, ideally with medical waste when possible. An added advantage to this method is that it prevents troops from collecting and misusing the bait. These bait stations work well when placed near latrines, showers, and waste disposal sites (burn locations, dump sites, etc.).

A stool sample with a mass of flies on its surface was chosen as the bait this was placed in a flytrap left in the area and left for 1 hour. To attract the attention of the flies, other piles of faecal matter were covered with sand, soil, leaves, or a wood during fly collection. Due to the strong sunlight and high temperatures during the day time in summer (July), most flies become somnolent and were easily collected in the collecting chamber and transferred to collecting tubes. In the community, rotten fish was used to lure and trap the flies.

 

Fly examination:

The flies were divided into 2 groups, as follow:

Flies from swamp, represented a homogeneous contamination of the fly population since they were exposed to the same source of infection. Helminths ova on the body surfaces, examined using manual shaking technique. Ten flies were pooled and stored in a test tube with formalin detergent solution (FDS), 200 flies were processed per test. Specimens were brought to the laboratory for processing.

Laboratory processing:

The collected flies were washing by manual shaking for 1 min. Detergent free helminth object from the body surface of the flies as it does faecal debris. The flies were removed by clean forceps and kept for identification.

The remaining preparation was centrifuged at 2000 rpm for 2 min. All sediments were examined under a light microscope for parasites.

Cockroaches collecting:

One hundred and seventy-eight cockroaches were collected, over a period of one year, 133 from different wards of houses of the village as the test group and 45 from residential areas, situated within 2 km premises from the study areas as the control group. The test group of insects captured (mostly at night time or early morning) from the floor of wards and kitchens, basements or bathrooms of residential areas.

Each cockroach was collected in a sterile test tube transported to the laboratory and anaesthetised by outing at 0oC for 5 min. examined under the dissecting microscope and identified using standard taxonomic keys.

For comparing control and test group, chi–square test was applied.

 

 

Isolation and identification of parasite from external surface:

After identification, 2 ml of sterile normal saline (0.9%) was added to the test tube and the cockroaches were thoroughly shaken for 2 min. Isolation of parasitic cyst was carried out by using 1 ml of washing which was centrifuged at 2000 rpm for 5 min. The deposit examined after staining with 1% lugols iodine under light microscopy and identified (28).

Isolation and identification of parasites from internal surfaces:

After external washing, cockroaches were placed in flasks rinsed with 70% alcohol for 5 min. (to decontaminate external surfaces as 70% alcohol is bactericidal). Transferred to other flasks and allowed to dry at room temperature. Cockroaches were then washed with normal saline for 2-3 min to remove traces of alcohol. Only cockroaches captured whole and live were utilised for the study. After being immobilised at 0oC, the gut of the cockroach was dissected out and macerated in 2 ml of normal saline. The resulting macerate was then processed in a similar way as described previously and the results recorded. For parasites ova / cysts, about 1 ml of washing was centrifuged at 2000 rpm for 5 min. and the deposit examined after staining with 10% lugol iodine under light microscope and identified (28).

Results:

Flies with helminthic objects on the body surface:

A total of 576 house flies (195 male & 381 female) were studied, all were identified as Musca domestica, and Chrysomya megacephala. 108 flies from the swamp area and 68 house flies in the community were studied. The results are shown in Table (1). Among 28 flies from the swamp area, 17 Hook worm eggs, 17 T. trichura & 1 Ascaris were detected (25.9%). The average egg count per positive fly was 1:3. Most flies carried only one egg on the body surface, while 17.9% and 7.1 % had 2 & 3 eggs respectively. In the community 8 house flies (11.8%) were contaminated with Hook worm & T. trichura eggs, the average egg count per positive fly was 1.0.

Faecal dots attached to the inner surface of the collection chamber were washed with FD solution and examined for helminths, this contamination occurred when the flies were trapped in the chamber. In the laboratory, the washing was processed by sedimentation method.

0.5 ml of sediment was obtained containing 27 T. trichura & 27 hook worms; the total number of eggs carried by the 508 flies in the swamp was derived from the pooled eggs from the sediment, egg in the two trials. The average number of eggs on the body surface of a fly was 0.4. Mites, the ectoparasite of the flies were also isolated from the body surfaces of the house flies, the number of mites per fly ranged 1-40.

Table 1: Transmission rate of flies in study area (July 2009)

Helminths eggs and Larvae

+ve flies

No. examined

Area

H. nana

Ascaris

T.trichura

H. worm

4

1

1

0

17

3

17

5

28 (25.9%)

8 (11.8%)

108

68

Swamp

Community

 

Table 2: Number of parasite eggs on the body surfaces of flies in the swamp area.

No. of eggs found

No. of flies

Trails

Total

H. nana

Ascaris

T. trichura

H. worm

121

0

34

86

 

400

Manual

35

0

1

17

17

108

Contaminat. rate

54

0

0

27

27

-

Washed sed.

210

0

2

78

130

508

Total

 

This study revealed that cockroaches trapped from different sites (toilets, parlours, kitchens and bedrooms) in the houses with pit latrines and water system shared the same parasites. The parasites included: cysts of Entamoeba histolytica, oocysts of C. parvum, C. cayetenensis and Isospora belli, cysts of Balantidium coli, ova of Ascaris lumbricoides, Anchylostoma deodunale, Enterobius vermicularis, ova of Trichuris trichura and larvae of Strongyloides stercoralis.

Medically important parasites were isolated from external and internal surface of 98% of test cockroaches and 8.9 % of control cockroaches.

Human parasites were isolated from test group of cockroaches showed adult E. vermicularis and 8 Ascaris eggs in two cockroaches but observation of control group did not show any parasite.

Table 3: Distribution of medical important parasites by sites and toilet facilities

No. of cockroaches studied

Source

Water system

Pit toilet

23

35

Toilets

22

27

Kitchens

11

17

Living-rooms

9

15

Bed-rooms

 

Parasites identified—Cysts of E. histolytica, oocysts of C. parvum, C. cayetenensis, Isospora belli, cysts of Balantidium coli, ova of Ascaris lumbricoides, Anchylostoma deodunalae, Enterobius vermicularis, ova of Trichuris trichura and larvae of Strongyloides stercoralis.

 

 

Table 4: Mean parasite count of cockroaches by site and toilet facilities

Water system

Pit toilet

Source

Mean parasitic count

Mean parasitic count

31

98 parasite/ml

Toilets

19

50

Kitchens

11

47

Living-rooms

11

38

Bed-rooms

 

 

Discussion

In the village, people did not consider parasites infection a serious problem, most did not submit stool for examination. Some infected cases refused to take anti- parasitic drugs. House flies, bush flies, and blow flies were common around the house holds, in garbage and in human and animal excreta. (29, 30, 31, 32). House flies is a proven mechanical transmitter of pathogens to human food (33). Ten intestinal helminth eggs and larvae has been isolated from flies collected around house hold, in an urban slum area, on an open defecation area, garbage heap, a small open air market, and meat butchers near human dwellings (29,30,31,34). Because the swamp was the p defecated area for the villagers, piles of faecal matter attracted flies. After feeding and resting, the flies travelled into the community, about 100 meters from the feeding site. Flies that had direct contact with parasite positive faeces were efficient carriers, because at least 25.9 % were contaminated with pathogens. In the defecation area every 2-3 flies carried at least 1 parasite on the body surface. After feeding, they rested in the area and contaminated the environment with the pathogens on their footpads, hairs, bristles, and external mouth parts.

An almost invisible dot of faeces in the environment might contain eggs or larvae that develop further and then transmit to humans. In this community 11.8% of flies had eggs on their body surface and could transmit them to human food, and household surroundings. 25.9% of infected flies had 2-3 eggs adhering to their body surface. The study found that 508 flies could leave 0.5 ml of faecal sediment in the collection chamber. This was considered to be the amount of pathogenic faecal matter distributed into the environment by 508 flies, thus, a fly carried 0.001 g faecal mass on the body surface after feeding on human waste.

We did not investigate the presence of parasites in flies’ guts. Nevertheless, many researchers have reported higher parasite detection rates in the gastrointestinal lumen than on body surface (29, 32, 35). Sulaiman et al. (31) found Hook worm eggs and larvae in the gut of flies, but found more on external surfaces. From this investigation it may be concluded that only one person with a light soil transmitted infection can contaminate both defecation areas and disease vectors. Over 25.9% of the fly population was contaminated. After resting and contaminating the environment with infective matter carried on the body surface, they transmitted the infection to the community, at the rate of 11.8%. The discovery of Ascaris lumbercoides eggs on the flies supported the supposition that house fly was a potential STH transmitter, which could carry and spread pathogens to other places, since they are able to travel up to 20 miles to unsanitary sites (36).

The current study showed that the housefly is a potential mechanical vector for parasite infection, and therefore its role in disease transmission should be not being under rated. In high risk areas, health education targeting the elderly should emphasize personal and environmental hygiene. In areas where open air defection is common, food must be strictly protected from houseflies, since in this study 11 flies around the house were found positive for helminth eggs. Other microorganisms causing bacterial infection have been reported (29). The control or eradication of houseflies should be attempted, to stop intestinal parasite transmission in the community, in addition to drug administration.

The results of the present study revealed contamination of almost all cockroaches collected from homes with different parasites which are significantly higher in comparison to control group. This shows the importance of cockroaches as carrier of parasitic worm, cysts, or eggs. There are some reports of the presence of parasitic forms on or in cockroaches (37). The finding of the present study showed the parasitic contamination in high numbers. The presence of E. vermicularis infestation indicates that the cockroaches had opportunity to get touch with infested patients or contaminated clothes which emphasises their vectorial potential for parasitic diseases (38).

Conclusions

Synanthropic insects such as flies and cockroaches can significantly contribute to the spread of food – borne parasites diseases in both developing and developed countries.

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