Epidemiological Study of dwarf tapeworm Hymenolepis nana in Najaf province / Iraq

The infection rate with Hymenolepis nana in Najaf province was 446 (1.79%) from the results of about 24.800 stool samples from different parts of Najaf province were examined by direct wet mount methodin Al-Sadder Medical City, Al-Hakeem Hospital, Al-Zahraa children and Maternity Hospital, Al-Menathera Hospital and Al-Sajad Hospital, in addition to medical centers and private clinics in province . This study was conducted during September 2013 to September 2014 . A questionnaire sheet, shown in appendix was filled for each individual studies . There was no significant difference (p< 0.05 )in the rate of infection between male and female and there was a significant difference (p<0.05) between infected patients (6-12 years) in comparison with other age distribution . It was found that 20% of 150 house mouse Mus musculus were infected with H.nana . The highest rate of the total infection was 7.34% in grain stores and the lowest rate (4%) in restaurants .


Introduction
Worldwide H . nana is found in tropics and subtropics; it most commonly occurs in children and in institutionalized people living in close quarters (1) . Transmission ofH . nana occurs by the fecal-oral route, accounting for higher prevalence in young children and adolescents with poorly developed hygiene skills (2) . Estimates of viability of H . nana eggs in the external environment range from 17 hours (3) to 10 days (4), suggesting the transmission of H . nana via environmental contamination may be lower than by the transfer of eggs on contaminated hands and / or food shared between children (4) . Accidental ingestion of an intermediate host infected with resting cysticercoid stage is an alternative host infected with the resting cysticercoid stage is an alternative route transmission (5), although this is considered a rare occurrence by some (6) . For this to occur, Tribolium beetles infected with Hymenolepis cysticercoids would have to be ingested by the definitive host (7) . Tribolium beetles may be present in flour stored over long periods of time at room temperature, representing a source of contamination of Hymenolepis spp . The practice of swallowing live beetles is a Chinese folk medicine remedy practiced in areas of Malaysia and has been reported as potential source of transmission for Hymenolepis infections (8) . This is unlikely, however, to represent a major source of infection unless this practices is widespread in areas endemic for the infection . The successful transmission of H . nana between hosts is reliant on a number of factors that effectively aid its dispersal in ''space and time'' . The continuous shedding of eggs (iteroparity) from the adult worms of H . nana is a factor that almost certainly aids its dispersal over time (9) . Furthermore, the development of resting stages (cysticercoids) in inset species enables H .nana to persist in the environment even when condition become unfavorable for the egg stage (9) . Importantly, if a definitive host is temporarily unavailable, the dispersal of H.nana can be effectively delayed without adverse effects . Other factors which may aid in the dispersal of H.nana include the well documented behavioral changes that some hosts exhibit when infected with parasite stages (10, 11, &12) . For example, (13) reports an increase in coprophagic activity of the grain beetle Tenebrio molitor when fed feces infected with eggs of the rat tapeworm H.diminuta . It has also been shown that beetles infected with cysticercoids of H.diminuta have impaired chemical defense mechanism and are more likely to be ingested by a definitive host than infected beetles (14) . Due to its capability of development via both an indirect life cycle H.nanahas the added advantage over other Hymenolepiasis in that it can adopt more than one strategy for transmission, a situation unique, with the cestodes, to this parasite (15) . Thus, H.nana increases its chances of dispersal over time by using alternative life cycle . This would greatly aid in the persistence infection in community even if 77 susceptible hosts of only one type were present . The aim of this study toevaluate the distribution of infection among patients in Najaf province .

Patients and Methods
About 24800 stool samples from different parts of Najaf province were examined by direct wet mount method in Al-Sadder Medical City, Al-Hakeem Hospital, Al-Zahraa children and Maternity Hospital, Al-Menathera Hospital and Al-Sajad Hospital, in addition to medical centers and private clinics in province . This study was conducted during September 2013 to September 2014 . Survey of infected house mice One hundred and fifty house mice, Mus musculus were trapped from different localities of province . Mice well killed, dissected and examined by opening the intestine in a Petri dish filled with normal saline or water, the worms allow relax, then examined and identified .

Results
Gender distribution A total number of patients infected with dwarf tapeworm in this study was 446(1.79%), confirmed by direct wet mount, 213 (47.75%), 233 (52.24%) for male and female respectively . There was no significant difference between male and female infection (P > 0.05) ( Table 1) .

78
The highest rate of infection was in summer, then followed by autumn, winter and spring . There was no significant difference (p > 0.05) between summer and other season (Table 4) .

Epidemiology of dwarf tapeworm in domestic mice
One hundred and fifty house mouse were trapped and dissected from different localities of province . It was found that 20% of them were infected with H.nana . The highest number of infection in mice were in grain stores 11(7.34) and the lowest percentage were in houses (Table 5) .

Statistical Analysis
The data were analyzed using the available soft-ware package . The results were presented as number, percentage whenever possible . The data were analyzed by using analysis of variance test taking p < 0.05 as the lowest limit significance according to (16) .

Discussion
Globally, H.nana is the most common cestode in humans (4) . The prevalence of H.nana is very common in countries with warmer, arid climates (17) and is endemic in many tropical and subtropical countries (4) . In this study, the prevalence of H.nana infections in Najaf province was 1.79% including infections in young children aged 4-14 years and also in adults of 20 years and above . A survey conducted of children indicated a prevalence of 1.6% of the total rate of infection (1.79%) with highest rates of infection found in children 6-12 years of age .H.nana is also common in rural and urban regions in Iraq and many areas of Najaf province . Rates of infection with H.nana in children and young adolescent are high . H.nana is the only cestode capable of completing its cycle without an intermediate host (18) . The direct life cycle can result in the establishment of heavy infections in mammalian host . This is due to the hermaphroditic nature of H.nana and the lack of a requirement for an intermediate host (9) . Thus, a single worm can potentially lead to the establishment of a large colony of adult worms within one host, as a result of self-fertilization (autoinfection) (9) . Furthermore, self infection (via faecal-oral contamination), especially in young children who may have poor hygiene skills (4) also contributes to the growth and maturation of more adult worms via the direct life cycle . The structure of the H.nana egg may be a useful adaptation to its direct life cycle, their hatching, increasing its close contact with mucosa, promoting its activation and delaying its expulsion from the host (19) . The arthropods such as the flour beetles Tribolium confusum and Tenebrio molitor were the most common intermediate hosts  (20) . Transmission of H.nana occurs by the fecal route, accounting for higher prevalence in young children and adolescent with poorly developed hygiene skills (2) . Estimates of the viability of H.nana eggs in the external environment range from 17 hours 90 (3) to 10days (4), suggesting the transmission of H.nana via environmental contamination may be lower than by the transfer of eggs on contaminated hand / or food shared between children (4) . Accidental ingestion of an intermediate host infected with the resting cysticercoids' stage is an alternative route of transmission (5) . In conclusion, the dwarf tapeworm requires no intermediate host . The house mouse is also common definitive host . Fleas and beetles can serve as transport hosts . Cysticercoid larvae can develop in the body cavity of these insects and are infective to either humans or rodents if accidentally ingested. Eggs in feces from infected mice and rats are a common source of human infection (1).