Excerpt
1. Introduction
1.1 Background
Cryptosporidium species are coccidian, oocysts forming apicomplexan protozoa. They complete their life cycle both in humans and animals, through zoonotic and anthroponotic transmission resulting in disease state called as Cryptosporidiosis. They are frequent agents of gastrointestinal infection in humans, domestic animals, and other vertebrates. Three species of Cryptosporidium have been associated with infection in cattle. Two small-type oocysts, C. parvum and C. bovis (Fayer et al ., 2005), infect the small intestine. However, the larger type, Cryptosporidium andersoni that infects the abomasum has been implicated as a cause of reduced milk production in dairy cattle (Lindsay et al ., 2000).
Cryptosporidium parvum is the most frequently detected pathogen in calves less than 3 weeks age (Moore and Zeman, 1991; Fuente et al ., 1999), where it considered being one of the main common causes of diarrhea at this age (Koudela and Bokova 1997).
However, Cryptosporidiosis should not only be considered from the perspective of animal health and production; its zoonotic character and the possibility that animals may act as a source of infection to humans, via foodstuff and water, should also be considered. Although the infection leads to few deaths, serious economic losses can occur due to costs involved in the treatment (Graaf et al ., 1999). Single infection with C. parvum is usually present in diarrheic calves; however, mixed infection with other pathogens exaggerates the problem (Vanopdenbosch et al ., 1979).
Cryptosporidiosis in water buffaloes ( Bubalus bubalis ) received great interest in different localities of the world (Galiero et al ., 1994; Dubey et al ., 1992). The prevalence of Cryptosporidiosis was also mentioned in African buffaloes ( Syncerus caffer ) among wildlife animals in Tanzania (Mtambo et al ., 1997). However, the risk factors concerned with Cryptosporidiosis in buffalo calves have not been described.
The Cryptosporidium spp . infection has been recorded in over 170 animal species in 50 countries (Snelling et al ., 2007) in wide range of vertebrate hosts and humans, particularly in children (younger than 5 years old) and immunocompromised persons (Xiao et al ., 2004). Cryptosporidium spp are transmitted via faeco-oral route. The oocyst is the infective stage that is exceptionally resistant to environment stress and harsh chemical treatments, which allows the parasites to stably persist outside a host (Fayer et al ., 1997).
1.1.1 Classification
Phylum: Apicomplexa
Class: Sporozoasida
Subclass: Coccidiasina
Order: Eucooccidiida
Suborder: Eimeriina
Family: Cryptospordiidae (Ramirez et al ., 2004)
1.1.2 Pathogenesis
Little is known about the pathogenesis of the parasites and no safe and effective treatment has been successfully developed to combat Cryptosporidiosis. According to (Ramirez et al ., 2004), the life cycle of most Cryptosporidium spp completed within the gastrointestinal tract (primarily small intestine and colon) of the host, with developmental stages being associated with the luminal surface of the mucosal epithelial cells. Thick-wall oocysts are excreted from the infected host in fecal material and represent the infective stage of the parasite. Infection of Cryptosporidium in a new host results from the ingestion of these oocysts, which release sporozoites that invade the epithelial cells and undergo asexual and sexual multiplication to produce thin-walled and thick-walled oocysts. Thin-walled oocysts can excyst endogenously, resulting in autoinfection, which helps to explain the mechanism ofpersistent infections (in AIDS patients) in the absence of successive (thick-walled) oocysts exposure.
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Figure – 1: Pathogenesis of Cryptosporidium .
Source: ( Putignani and Menichella, 2010)
1.1.3 Epidemiology
Unlike other intestinal pathogens, Cryptosporidium can infect several different hosts; can survive in most environments for long period of time due to its hardy cysts (Ramirez et al ., 2004). It is an inhabitant of all climates and locales. In majority of cases the Cryptosporidiosis is diagnosed due to the presence of the oocysts and antigen in the faeces. Transmission of Cryptosporidium mainly occurs by ingestion of contaminated water (e.g. surface, drinking or recreational water), food sources (e.g. chicken salad, fruits, and vegetables) or by person-to-person contact (community and hospital infections). Zoonotic transmission of C. parvum occurs through exposure to infected animals (person-to-animal contact) or exposure to water (reservoir) contaminated by feces of infected animals (Putignani and Menchella, 2010).
illustration not visible in this excerpt
Figure – 2: Epidemiology of Cryptosporidium
Source: ( Putignani and Menichella, 2010)
Over 20 methods of staining aiming at the oocysts identification is applied in the microscopic diagnosis. However the microscopic methods frequently fail in the diagnosis of asymptomatic infection requiring the need of molecular techniques.
1.1.4 Transmission pattern
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Figure – 3: Transmission pattern of Cryptosporidium spp.
1.2 Justification of the study
There is no single study regarding prevalence of cryptosporidiosis in wild water buffalo in Nepal, this study endeavors to bridge the knowledge gap in concerned field. Since the population of wild water buffalo is small and vulnerable, this kind of study helps towards the conservation efforts.
It is a guideline in our wild and domesticated buffalo population as it indicates the protozoan parasites infestation. Though the exact mortality of younger calves, primarily the suckling ones is yet to be known. Cryptosporidiosis may be one of the killer diseases in young ones in our context.
1.3 Objectives of the study
1.3.1 General objective
- To study comparative prevalence of Cryptosporidium species in wild water and domestic buffaloes in Koshi Tappu wildlife reserve, Nepal.
1.3.2 Specific objectives
- To know the prevalence of Cryptosporidium in wild water and domestic buffaloes in Koshi Tappu Wildlife reserve, Nepal
- To make comparative analysis of the occurrence of Cryptosporidium in different seasons.
1.4 Limitations of the study
- The study is just a cross sectional study. So the results can only be related to a point of time and this cannot be related to a period of time.
- Sample size and the species are limited due to which the results cannot be generalized for the entire population of the species in that area.
- The individual difference of the animals like immunity and resistance, among the animals may have some effects on the study.
- Genotyping for the species identification could not be done from the positive samples.
2. Literature review
Venu et al ., 2012 investigates prevalence of Cryptosporidium through molecular methods and found 39.65% prevalence in the southern states of India with predisposition in females than males and in young age.
Siwila and Mwape, 2012 used similar methods as this research and found out the total prevalence to be 44.4 % with the presence of parasite in every farms investigated.
Jeníkova et al ., 2011 identified two species, C. suis and C. pig genotype II as major causative agent of the cryptosporidiosis in piglets. It was further indicated that the C. suis was found in all 1-12 week age piglets whereas, Cryptosporidium pig genotype II was recorded only in animals older than 6 week of age.
Chen et al ., 2011 identified Cryptosporidium in all 12 pig farms under study and varying in the prevalence from 14.1 to 90.6%.
Ghimire et al ., 2010 reported a case of Cryptosporidium infection from environmental contamination in swimming pools in Nepal.
Among animals, the wild animal had the highest prevalence and was observed in deer which was 71% and followed by rhino 25%. The calves and buffalo calves were suffering from 34 and 37% respectively (Karna, 2010).
Khan et al ., 2010 identifies age related pattern of the Cryptosporidium infection and also the C.hominis , C. parvum and C. bovis were identified from farm workers in India which clarifies a potential risk of zoonotic transmission between cattle and humans on dairy farms.
Amatya et al ., 2010 identified 4.4% prevalence in the HIV seronegative children from eastern region of Nepal. Ghimire, Mishra and Sherchand, 2005 identified
Cryptosporidium in 11.3% of 9000 stool samples. They found out 16.7% positive in washings of radishes, 3.3% in cauliflower, and 13.3% in washings of mustard leaves washed in the rivers of Kathmandu. Furthermore, 13.0% in sewage water, 9.0% in river water and 0% in pond water and 1% in well water was demonstrated. Dhakal et al ., 2004 identified C . parvum in 10.4 % children from Kanti children hospital.
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