Prevalence and Associated Risk Factors of Myiasis in Different Areas of Chittagong , Bangladesh

Received: Revised: Accepted: 2013–12–24 2014–01–18 2014–01–20 A One year eventual study was conducted to detect the prevalence and feasible risk factors of myiasis in various species of animal in different areas of Chittagong, Bangladesh from March 2012 to February 2013. By Cross–questioning over animal rearers and with clinical examinations myiatic cases were identified and varied risk factors were distinguished. 226 cases were noted manifesting signs of myiasis. Prevalence rates were goat 69% and cattle 22%; wherever seasonal prevalence was explored highest in autumn (55.5%) than cold (11.6%) (p>0.05). Statistically significant difference in the prevalence was reputed with breed, age, sex, wound depthness, temperature and attitude of animal (p ≤0.05). Above 6 months aged animals (75.5%) and cross breeds (34.2%) were mostly infected where females (64.5%) were more prone to myiasis. Foul odorous abscess with wound, breach after delivery, umbilical infection, dirtiness, fecal and urine contamination, bed sore were the most habitual risk factors, though findings were not significant (p >0.05). Most exposed sites were vagina and perineal region, inter digital space, tail, brisket, navel, scrotum, inguinal region and gum. The study has remarked probable health hazards caused by flies in animal that will promote animal rearers in avoiding and clinically managing them. Additional widespread studies are suggested as molecular identification of species of flies and economic analysis caused by myiasis. All copyrights reserved to Nexus® academic publishers


INTRODUCTION
Myiasis (myia is Greek word for "fly" Shinohara et al., 2004) is the infestation of vertebrate animals with dipterous fly larvae, feed on the host's dead or living tissue, liquid substances, or ingested food for a period of time (Serra-Freire and Mello, 2006).Entomologically (biological relationships of causative fly species and hosts), it may be classed as obligatory or specific, facultative or semi-specific and accidental (Catts and Mullen, 2002;Jelinek et al., 2000).Clinically, it can present as cuticole, cavicole, gastricole, anal, genitor-urinary, nasopharyngeal, ocular and aural depending on anatomical site due to eggs or larvae of dipteran fly laid on the wounds or nasal, oral, genital and aural cavities (Sherman, 2000).Flies that caused myiasis belong to the families Calliphoridae, Sarcophagidae, Hypodermatidae, Oestridae and Gasterophilidae especially.However, some other species belonging to the families such as Muscidae, Psychodidae etc. may cause myiasis rarely (Serra-Freire and Mello, 2006).It is a worldwide infestation with seasonal variation.Its incidence rate is higher in tropics, south-east Asia and subtropics of Africa; where warm and humid climate prevail almost throughout the year and causative factors are exposure to myiasis-causing flies and their increased aggressiveness (Bolognia et al., 2008).Fairly it is common in cattle in field condition particularly in the season of fly prevalence (John, 1999).So, most frequent host is cattle and goat (46.4%), followed by dogs (15.3%), humans (14.7%), pigs (6%), horses (4%) and sheep (1%) (Sergio et al., 2007).
Wounds, soreness and laceration, breach after delivery, urine and fecal contamination, cleanliness and sanitary condition, wetted fleece or hair, lack of aseptic surgery, bacterial skin contamination with foul odor etc. are still conventional as the major predisposing factors for myiasis (Myiasis Wiki vet, 2011).Infestations of its cause irritation (biting and rubbing the affected sites), annoyance to animals; disruption of normal habits including resting, feeding and digestion which has leading role to retard growth, loss of weight and reduced milk and meat production etc. (Otranto et al., 2004).In Bangladesh, Rahman et al. (2009) conducted a study on clinical evaluation of different treatment regimens for management of myiasis in cattle.However, so far, very limited research was initiated with a view to consider

Prevalence and Associated Risk Factors of Myiasis in Different Areas of Chittagong, Bangladesh
prevalence and feasible associated risk factors of myiasis in Bangladesh.Therefore, the present work was anticipated to explore the prevalence and risk factors of myiasis in various species of animals in different areas of Chittagong, Bangladesh; to revise the episode of myiasis in the species with respect to age, sex, breed, season and predilection site etc; to look over the depthness of myiatic wounds.

Questionnaire Design and Data collection
A closed ended (categorical) Questionnaire was designed according to Thrusfield (2005).Repeated questioning was performed over animal rearers, observation of animal and taking records.Data were recorded including affected animals, species, breed, age, sex, body condition, weakness, onset and duration of illness, affected sites of myiasis, frequencies of larvae and associated risk factors from March 2012 to February 2013 where seasons: summer (Mar 2012 to May 2012), rainy (June 2012 to Aug 2012), autumn (Sept 2012 to Nov 2012) and winter (Dec 2012 to Feb 2013).Other information sought including deworming, vaccination, pregnancy status, parity, housing pattern, floor (Katcha/ dirty/ muddy/ brick/ concrete/ rubber bedded), rearing system (intensive or semi-intensive or free range) as well as system of grazing or zero grazing.

Myiasis According to Risk Factors
Wounds with foul odor, swelling, vesicle and abscess by bacterial contamination were the most crucial risk factors for myiasis.However, breach after delivery in cows, umbilical infection in new born kids, insanitary and germinfested infrastructure of housing leads to bed sore were the most significant risk factors.Additionally, dirtiness and wetted surroundings (fleece, hair) with fecal and urine contamination, lack of aseptic surgery like castration with unsterile instruments (scissors, scalpel, forceps etc.), accidental injury (nail, barbed wire, glass etc.) as other major risk factors was evaluated.Furthermore, various diseases such as FMD (Foot and Mouth Disease), foot rot, contagious ecthyma, aural hematoma were complicated with myiasis.It was also experiential that, animals, were bitten by rat or dog (carnivores) create space on that biting place predisposed to myiasis.Amazingly, gangrene, wart, polyps were further recorded risk factors of myiasis (Table 2).

Comparison of Myiatic wound between Cattle and Goat
Among all wounds (Incised, septic, lacerated, punctured etc.), septic wounds were found more prominent than ISSN 2308-2798 others (Cattle 69.4% and Goat 55.5%) while incised wound was recorded as persistent in goat than cattle (Cattle 6.1% and Goat 19.36%).

Myiasis According to Affected Body Regions
Myiasis was observed regardless of body area though vagina and perineal region, tail, inter digital space, brisket region, navel, scrotal region, inguinal region, udder, thigh/rump, limb, head region, mouth/gum, nasal, ear and neck region were recorded more vulnerable.Details of myiasis affected regions are illustrated in Table 3.

DISCUSSION
Overall prevalence of our study was 5.21% among 4338 cases which is comparable to Giangaspero et al. ( 2011), Alahmed (2004)    On the observation, dirtiness with fecal and urine contamination, poor housing infrastructure, floor with rough surface (brick, concrete) leads to bed sore and wound which is agreement with Bhola et al. (2012).Phillips (2009) confirmed sheep were predisposed to fly strike (cutaneous myiasis) where fleece was contaminated with feces or urine.Accidental injury and traumatic wound (nail, barbed wire, glass etc.) is another important risk factor causing myiasis.Our study revealed that myiasis was found highest in autumn (55.5%) than cold (11.6%) due to prevailing warm and humid climate of tropic where Radfar and Hajmohammadi (2012) reported prevalence varied from 6.8% to 41.8% in August, 2007 to February, 2008 in Southeastern part of Iran; Paredes-Esquivel et al. ( 2012) recorded significant differences in prevalence in winter and autumn where fly activity held between May to June in the island of Majorca (Spain).In addition, Shoorijeh et al. (2011) found prevalence ranged from 6.6% in spring to 17.9% in winter in South Iran where Abd El-Rahman (2010) analyzed infestation rate in camel was significantly greater in colder (68.8%) than warmer (31%) in Western Libya.Similarly, Orfanou et al. (2011) found six cases from May to July and three cases from August to October in 163 dogs.Alem et al. (2010) described prevalence ranged from 77.7% to 98.8% from November to March in sheep and goats in Central Oromia; Arslan et al. (2009) reported prevalence of nasal myiasis was 54.3% in spring, 41% in summer, 28% in rainfall, 38.9% in winter and statistically significant differences among seasons (p ≤ 0.05) at north-eastern part of Turkey; Alahmed (2004) stated highest percentages of myiasis during Mar-May (60%) and Sept-Nov (31.5%)where temperature and relative humidity are optimum and infestation incidences were low (5% and 1.5% respectively) at dry hot season (Jun-August) and cold season (Dec-Feb) in Riyadh Region; Dorchies et al. (2000) found prevalence from 14.3% to 65% in Feb-Oct in sheep and 6.25% to 47.1% in Sept-Apr in goat in France; Farkas and Hall (1998) described myiasis season lasted from March to November where most cases were available in July and August at sheep, cattle and horses in Hungary; Amin et al. (1997) revealed high infestation rate in summer, followed by spring then autumn.However, Cramer et al. (2002) said no month of the year presented higher occurrence of myiasis cases.

CONCLUSION
Myiasis is the most familiar and widely distributed disease in Chittagong, Bangladesh.This research has addressed the problem of myiasis in Bangladesh, particularly in Chittagong, so that they will take necessary measures to make the problem subside, animal owners or rearers in avoiding and clinically managing them as well.Further widespread studies are suggested as molecular identification of species of flies and economic analysis caused by myiasis.
Fig 1: Myiatic wound at perineal region of a goat (Date: 01.12.2012) Trombetta et al. (2009) reported traumatic myiasis habitually in cattle, dogs and cats whereasFarkas and Hall (1998) found traumatic myiasis infestation >10% of animals at sheep, cattle and horses in Hungary.Additionally, Dik et al. (2012) found 22 traumatic myiasis in animals in Turkey; Ipek DN and Ipek P (2012) observed a facultative traumatic myiasis in domestic rabbit; Giangaspero et al. (2011) examined 10 traumatic myiasis in Italy.Scholtz et al. (2011) reported as presence or absence of dermatophilosis was the main predisposing factor for blowfly strike in sheep.Amazingly gangrene, wart, polyp are fascinating risk factors of myiasis.

Table 1 :
Association between different variables with the presence of larva causing myiasis in goats tested using Chi square (χ 2 ) test Radostits et al., 2000.ExaminationCase was identified with owner's complaint, history of weakness, onset and duration of illness, identification of feasible risk factors and clinical examination of animal.General attitude (alertness/ dullness/ depression) and body condition of animal (Cachectic/ poor/ fair/ good/ fat/ over fat) were carefully inspected by distant inspection asRadostits et al., 2000.In addition, posture and gait (normal/ defective) were examined.Animal was closely examined by parting of hair/fleece; light palpation and close direct inspection to detect hair coat, skin abnormalities, skin lesions (foul odorous discharge, crusts, scale and dandruff), distribution of maggots were recognized.Myiatic wound(s) identified by inspection and categorized wound whether it might be septic/ lacerated/ incised/ punctured/ perforating/ abrasions/avulsion/hematoma.Maggots of flies explored ISSN 2308-2798 through inspection and removed from wound(s) by using tissue forceps or artery forceps.In addition, depthness (deep or superficial) of wound was determined using metal probe or forceps.Finally, frequency of larvae was resolute accordingly as few larvae (<15 in number)/ moderate (15-40)/ a lot of (>40 in number).Data AnalysisData that were collected been entered into MS excel (Microsoft office excel-2007, USA).Descriptive analysis was through by STATA version-12.1 (STATA Corporation, Texus, USA) to estimate the association between a categorical explanatory variable with outcome and then Chi square (χ 2 ) test was performed.An association was regarded as significant if p ≤ 0.05.RESULTS226 myiasis cases were evaluated from approximately 4338 different cases where the highest number of cases in Chittagong Metropolitan Area (195 cases) and lowest numbers at Rangamati (2 cases).Different species were signed with myiasis [155 goat (69%), 49 cattle (22%), 15 dogs (7%), 5 sheep (2%), 1 monkey and 1 rabbit] whether 86 animals were male (38%) and 140 animals were female (62%).Three age groups were categorized accordingly above 6 months old (170 animals), less than 6 months old (51 animals) and exactly 6 months old (5 animals).Various explanatory variables of goat i.e. breed, age, sex, depthness of wound, temperature, attitude were significantly associated (p ≤ 0.05) with myiasis (Table1

Table 2 :
Comparison of myiasis among goat, cattle and others according to risk factors