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Occurrence of human hepatitis E virus in Norway rats: A zoonotic potential with great public health implications

Occurrence of human hepatitis E virus in Norway rats: A zoonotic potential with great public health implications Nahed Hamed Ghoneim, Khaled Abdel-Aziz Abdel-Moein, Dalia Anwar Hamza, Naglaa Mohamed Hagag Department of Zoonoses, Faculty of Veterinary Medicine, Cairo University, Cairo, Egypt National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Cairo, Egypt Asian Pac J Trop Dis 2016; 6(9): 718-721


Introduction
Hepatitis E virus was firstly recognized in 1978 after large epidemic of hepatitis in Kashmir Valley while the virus was sequenced in 1990 to be genetically recognized [1]. Nowadays, hepatitis E is considered one of the most important enterically transmitted viral hepatitis affecting humans throughout the world. The virus is endemic in many developing countries where outbreaks usually occurred whereas sporadic form of the disease is more common in the developed ones [2]. Hepatitis E virus is a single stranded positive sense RNA virus belonged to genus Hepevirus, family Hepeviridae. To date, hepatitis E virus can be classified in to four genotypes I-IV with characteristic geographical distribution, genotype I in Asia and North African countries but Central Africa and Mexico for genotype II; America, Europe and Japan for genotype III while genotype IV was exclusively present in Asia [3]. The global burden of hepatitis E was estimated to be 2 billon out of total human population (6 billion) and most of them were concentrated in countries of poor resources [4]. In addition, according to World Health Organization records, annually there are more than 20 million hepatitis E virus infections with 3 million acute cases and about 56 000 related to deaths [5]. Hepatitis E infections usually manifested as acute viral hepatitis including fever, malaise, icterus, hepatomegaly and elevated liver enzymes with low mortality rate (less than 1%) while the disease is extremely serious in pregnant women with high case fatality rate which may reach 25% [6]. is not well-known. Hepatitis E virus genotype I and genotype II were strictly infect humans whereas genotypes III and IV infect both humans and animals [7]. The main mode of transmission is thought to be fecal-oral route especially via contaminated water as many large water-borne outbreaks were reported meanwhile the zoonotic route of transmission was proposed after the detection of hepatitis E virus in pigs [8]. Recently, the virus has been detected in a wide range of animal species rather than swine including boars, deer, sheep and rabbits to expand the zoonotic spectrum of the virus [9]. Consequently, the zoonotic transmission of hepatitis E to humans has gained ground and it was assumed to be taken place either through direct contact with infected animals or ingestion of contaminated food of animal origin [10]. Curiously, undercooked meat from infected animal reservoirs such as pigs, deer and wild boars were incriminated to be sources of hepatitis E infections to underline the importance of the zoonotic route in the epidemiology of hepatitis E virus among humans [11]. Moreover, in recent study that was conducted in Egypt, the seroprevalence rates of the hepatitis E antibodies among farm animals were 21.6%, 14%, 4.4% and 9.4% for cows, buffaloes, sheep and goats respectively which may point out to the potential role of animals in the epidemiology of hepatitis E in Egypt [12]. In contrast, the recent identification of

Animal samples
Fecal samples were collected from the recta of 43 Norway rats [Rattus norvegicus (R. norvegicus)] after they were anesthetized and humanely killed via cervical dislocation [14]. All rats were trapped from rural districts of Giza and Fayium governorates, Egypt. Moreover, fecal samples were gathered from 30 apparently healthy sheep. All animal samples were inserted in sterile tubes and kept at -80 °C till processed.

RT-PCR step
The

Nested PCR step
Nested PCR was done using the DNA products of the former RT-PCR as DNA templates to confirm hepatitis E virus genotype I using the following set of primers: forward one: 5'-ATG ACT TTG CTG AGT TTG ACT-3'; reverse one: 5'-CAT ATT CCA GAC AGT ATT CC-3'. The reaction was done using EmeraldAmp® GT PCR master mix (Takara, Japan) and the procedure was done according to Zhao et al. [15] while specific bands for hepatitis E virus genotype I were noted at 218 bp after electrophoresis step.

Results
Out of 73 examined animals, 5 yielded human hepatitis E virus genotype I in their feces giving an overall prevalence 6.8%. Only rats yielded positive results with prevalence 11.6% whereas none of sheep samples was positive (

Discussion
In the last few years, hepatitis E virus has emerged to be one of the leading causes of acute viral hepatitis with a global impact nevertheless knowledge about its epidemiology is still limited.
The zoonotic potential of hepatitis E virus is strongly proposed especially in rural communities where animals and humans usually share the same habitat. In Egypt, hepatitis E virus genotype I is the circulated hepatitis E virus genotype and has been detected among human patients [16,17].  ) and pointed out the possibility of rats to be potential reservoirs for such zoonotic hepatitis E virus genotype [19]. Therefore, the results of the current study highlighted the potential role which may be played by rats in the epidemiology of hepatitis E virus, a matter which has great public health implications. Noteworthy, Norway rat is a common inhabitant in rural settings in many countries and has the ability to access surface water to contaminate it through shedding of hepatitis E virus bearing in mind that hepatitis E virus is a water-borne virus and contaminated water stands behind many human infections [9]. Accordingly, infected Norway rats may contaminate irrigated water and consequently the virus may contaminate fresh produce and thereby reach human gut [20].
Furthermore, hepatitis E virus was previously detected in sewage [21] and whenever sewage is a common habitat for Norway rats (also called sewer rats) so that they may easily contract the infection from sewage and disseminate hepatitis E virus elsewhere during their daily activities considering hepatitis E virus is stable in soil for several weeks at environmental temperature [22]. Importantly, Norway rats may get entered human houses in rural settings and whereby contaminate house garden, households and human foodstuffs a matter which is of special concern for children in such settings antibodies among children reach 60% [25]. Our results indicated that children in rural settings may be exposed to hepatitis E virus in their early life due to poor sanitation or contaminated households.
These results were agreed with that obtained by Aboulata et al. (2005) who concluded that in Egypt children was early exposed to hepatitis E virus and the seroprevalence of hepatitis E virus IgG increases with age [28]. In conclusion, the results of the current study provided concrete evidence on the ability of Norway rat to acquire and disseminate human hepatitis E virus genotype I under natural conditions. Therefore, Norway rat should be considered as a potential reservoir for such hepatitis virus especially in rural settings where the disease is more prevalent.