ABSTRACT
Cryptosporidium is an apicomplexan parasite known to cause gastrointestinal disease in humans and several animal hosts including piscines. To determine the occurrence of Cryptosporidium in catfish, Clarias gariepinus, and their aquatic habitats from the wild and cultured environments, 400 catfish from two dams (n = 100) and six backyard catfish farms (n = 300) as well as 40 water samples of 20L each from the dams (n = 10) and 10L each (n= 30) from six backyard farmswere examined in Zaria, Kaduna State, Nigeria. The fish gut contents were concentrated using formol-ether concentration technique, whilst the water samples were concentrated using sedimentation and centrifugation techniques. All processed samples were stained with modified Ziehl-Neelsen method and morphometric measurements of oocysts taken with the aid of a calibrated eyepiece graticule. One hundred questionnaires were also administered to catfish consumers within the study area, this was to obtain information on their level of awareness on diseases associated with catfish and their hygiene practices after handling catfish. Basic objectives of this study were to determine the followings; the prevalence of Cryptosporidium in catfish and its water habitat, the effect of the physico-chemical parameters of the water habitat of catfish on occurrence ofCryptosporidiumin water sampled within study area, as well as the association between the prevalence of Cryptosporidium in Clarias gariepinus and management practices of catfish farmers in the study area.Cryptosporidium oocysts were found in 86 (21.5 %) out of the 400 fish, and 3 (7.5 %) out of the 40 water samples with oocysts of 3 different size ranges, corresponding to the following species; molnari –50.0 % (4.69 µm ± 0.07 × 4.46µm ± 0.29), C. parvum – 45.3 % (5.05µm ± 0.12 × 4.49 µm 04), and C. andersoni – 4.7 % (7.40µm ± 0.47 × 5.60 µm ± 0.49). Of the four physico-chemical parameters (temperature, pH, dissolved oxygen, and turbidity) measured, only turbidity was found to have a significant effect (P < 0.05) on the occurrence of Cryptosporidium in water sampled within the study area. Wild catfish were significantly more infected with Cryptosporidium oocysts than the cultured ones (OR = 1.962; 95% CI 1.204 < OR < 3.196; P = 0.0078). Cryptosporidium oocysts were higher (10.0%) in dams as compared to 6.7% in water from backyard farms. The prevalence of Cryptosporidium oocysts in the bigger catfish within 451 to 850g was 28.0% compared to 21.1% in the smaller ones that were within 150 to 450g. Similarly, the prevalence was slightly higher (22.2%) in the lengthier (36 – 55cm) catfish than in the smaller ones (21.1%) within 15 – 35cm in length. The prevalence was also higher in male catfish (24.4%) than in females (19.2%). Based on management practices of catfish farmers, frequency of pond water replacement (P = 0.0008) and method of dead fish disposal (P = 0.04) were significantly more commonly associated with the occurrence of Cryptosporidium in backyard farms, whereas, type of pond, source of water, frequency of cleaning ponds and prophylactic medication to fish were not significant (P > 0.05). A significant number of the catfish consumers were unaware of any disease associated with catfish consumption (70.0%) or the zoonotic risks of any disease of catfish (86.0%). The presence of Cryptosporidium oocysts in catfish and their water habitats in the study area is of public health concern indicating the possible health threats posed to consumers and handlers.
CHAPTER ONE
1.0INTRODUCTION
1.1 Background of the Study
Cryptosporidium is a protozoan parasite that is widespread among vertebrates causing mainly gastrointestinal disease in mammals and reptiles and enteric, renal and respiratory disease in birds (Chalmers and Giles, 2010). Although, infections have been reported in fish and amphibians, the disease has not been well described (Chalmers and Giles, 2010). Due to the wide host range of this parasite, cryptosporidiosis has been considered to be a zoonotic disease for some time now (Xiao and Feng, 2008). Species definition and identification of this genus is constantly changing, with the addition of “new” species based primarily on molecular criteria (Xiao and Feng, 2008). Currently, 32 species ofCryptosporidiumare considered as valid species (OIE, 2016). Cryptosporidiumspp recognized aspiscine species include;Cryptosporidium molnari, C.huwi and C. cichlidis(Rona et al., 2011; Certad et al., 2015; OIE, 2016).
The first case of human cryptosporidiosis was first described in 1976 in a three and a half year old girl who developed self-limited enterocolitis (Nime et al., 1976). By the early 1980s, outbreaks among veterinary students and workers demonstrated the risk to animal handlers (Current et al., 1983; Jakipii et al., 1983) and later a massive water-borne outbreak in Milwaukee, Wisconsin in 1993 was reported by Mackenzie et al.(1995a).In developing countries, Cryptosporidium infections occur mostly in children younger than five years, with peak occurrence of the infections and diarrhoea in children younger than two years (Bhattacharya et al., 1997; Bern et al., 2000). This is particularly because of the independent and synergistic effects of immune naivete, malnutrition and HIVinfection (Siobban and Saul, 2008). Children can have multiple episodes of cryptosporidiosis, indicating that acquired immunity to Cryptosporiidum infection is short lived or incomplete. Early childhood cryptosporidiosis has been associated with subsequent impairment in growth, physical fitness and cognitive function (Siobban and Saul, 2008). The organism is highly infectious with a medium infective dose (from human trials) of only 132 oocysts, and 20% of human subjects could be infected with as few as 30 oocysts. The oocysts are highly resistant to inactivation in the environment and there is however, no chemical method of inactivation to kill the organism in drinking water (Quiroz et al., 2000).
Transmission is faeco-oral, either through direct contact with infected hosts or through multiple vehicles including changing diapers, drinking water and food (Casemore, 1990). Understanding the hosts, sources of infection and transmission routes is vital for the control of this parasite for which specific treatment options are limited and vaccines lacking (Chalmers and Giles, 2010). Diagnosis is normally established by conventional microscopic methods and the modified Ziehl Nelseen (mZN) or auramine phenol (AP) methods using un-concentrated faecal smears (Casemore et al., 1985; Casemore, 1991). The species of Cryptosporidium responsible for infection can be determined by PCR-RFLP or sequencing of Cryptosporidium DNA isolated from oocysts (Coupe et al., 2005).
Fish is one of the important sources of protein for humans and other animals in thetropics. According to FAO (1989), fish accounts for more than 40% of the protein diet of two-thirds of the global population. Fish does not only provide food for immediate consumption, but people rely on fishing for economic gains and job provision. A well processed fish product from the tropics has a ready market in developed countries and is therefore a good foreign exchange earner (Imam and Dewu, 2010). Like other animals, fish is also afflicted by endo- and ectoparasites, especially protozoans and helminths causing heavy morbidity and mortality (Al-Murjan and Abdullahi, 2008).Clarias gariepinus commonly known as African catfish has been widely introduced around the world. These species are found as far as South Africa and Northern African regions. They have also been introduced in Europe, the Middle East, and parts of Asia. They are potamodromous, which means they migrate within streams and rivers. They are elongate with fairly long dorsal and anal fins. The dorsal fin has 61-80 soft rays and the anal fin has 45-65 soft rays. African catfish are subjected to a wide variety of diseases including bacteria, fungi and miscellaneous parasites (Madu et al., 1999).
1.2 Statement of the Research Problem
Cryptosporidium is one of the causes of diarrhoeal illness in man and animals worldwide (Xiao et al., 2001a; Xiao and Feng, 2008; Maikai, 2009), and several groups of humans are particularly susceptible to it.In industrialized countires, epidemic cryptosporidiosis can occur in adults by food borne or water borne routes (Millard et al., 1994; Mackenzie et al., 1995b; Quiroz et al., 2000). In immunocompromised persons, the incidence and severity of cryptosporidiosis increases as the CD4+ lymphocyte cell count falls, especially when it falls below 200 cells/µl (Quiroz et al., 2000). Inseverely immunocompromised patients, disease can progress to cholangitis or pancreatitis and the infection is frequently chronic and can eventually become lethal, second only to tuberculosis, thus, cryptosporidiosis is the main terminal disease in HIV infection (O’connor et al., 2011).Two genotypes are the most common causes of human cryptosporidiosis, and these are the zoonotic C. pestis (or the C. parvum “bovine genotype”) and the human-specific C. hominis (or the C. parvum “human genotype”) (Fayer, 2010).
Parasitic diseases of fish are of particular importance in the tropics. Parasites usually exist in equilibrium with their host as a survival strategy. However, in instances where hosts are overcrowded such as in aquaria or in fish farms, parasitic diseases can spread very rapidly causing high mortality. Fishes have been reported to be affected by some zoonotic organisms such Mycobacterium, in addition to which several protozoan parasites such as Ichthyophthirius multifilii have also been reported. Currently, three Cryptosporidium species are recognized in fish hosts namely: C. molnari, C. scophthalmi and C. huwi(Rona et al., 2011, Yang et al., 2016, Costa et al., 2016); other species such as the zoonotic Cryptosporidium parvum as well as C. xiaoi and C. hominis have also been reported in fish hosts(Koinari et al., 2013; Ryan and Xiao, 2014; Certad et al., 2015). Nonetheless, not much is known about Cryptosporidium species infecting piscine hosts, although it is known to cause high morbidity and a veriety of clinical signs (Alvarez-pellitero et al., 2004; Ryan and Xiao, 2014; Ryan et al., 2015; Yang et al., 2015).
The African catfish Clarias gariepinusis a major tropical aquaculture species in Africa and the most popular with fish farmers and consumers in Nigeria. The total current catfish consumption in Nigeria according to the Farmers Association of Nigeria is about 1.5 million metric tons annually. Fish consumption is however, not devoid of risks due to the possibility of fish harbouring infectious or pathogenic microorganisms, particularly if such organisms are zoonotic (Leal et al., 2008). Fish is an aquatic organism that can be processed into food for humans and animals;hence there are possibilities of parasitesharboured by fish to be transmitted to consumers and processors following improper cooking and careless handling, respectively. Cryptosporidiosis is an emerging zoonotic gastroentericdisease that is known to occur in many animal species (Ayanda, 2009), including wild and farmed fish worldwide.Several reportshave confirmed the cosmopolitan nature of Cryptosporidiumspecies in surface water, groundwater, estuaries, and seawater. Itstransmission is through its hardy oocystswhich are passed in the faeces with water as its major vehicle of transmission. Thus, zoonotic transmission of cryptosporidiosiscan occur from consumption of fish obtained from contaminated water (Leal et al., 2008). In Nigeria, Maikai (2012), Atawodi and Bichi (2013) have reported the parasite in catfish. However, there is still need to investigate these findings further in relation to the fish habitat (water) and management practices of farmers as well as the level of awareness of the parasite among consumers in Zaria.
1.3 Justification of the Study
Fish is becoming an important component of people’s diet in many parts of the world. This is probably due to its palatability, leanness, and possession of healthy Omega 3 fatty acids (Atawodi and Bichi, 2013). Realizing the importance of fish to human nutrition and its contribution to the national income makes it important to establish and strengthen aquaculture and fisheries programmes(Chilima,2007), which is one of the reasons for the popularity of fish farming in Nigeria and around the world(Bernard, 2009). The importance attached to the culture of catfish in Nigeria is not only because it is a highly esteemed species that command high market value, but it is hardy and survives where most other cultivable species cannot (Maikai, 2012). Zaria is located in the North-West part of Nigeria where extreme weather conditions can be experienced. This could be a reason for catfish being a major cultivated fish species in the area. The presence of fish ponds and several catfish retail outlets in Zaria is also an indication that the town is not left out in the global increase in catfish culture and consumption. Furthermore, some families engage in backyard catfish farming as a means of income supplementation. Thus, there is need to embark on this study to determine the various management practices in backyard catfish farms that may be associated with the occurrence of Cryptosporidium in cultured catfish and their habitats in Zaria.
Cryptosporidium has been reported as a prime candidate in transmission of water borne illnesses. It has also been found to be ubiquitous in surface waters and extremely resistant to various environmental pressures and chemical disinfectants (Perz et al., 1998). Since Cryptosporidium has been reported in some animal species and vegetables within the study area, it is therefore, important to check the aquatic habitat in order to determine the possibility of a transmission circle occurring in the area, which could serve as an indicator of the risk of exposure of human populations of contracting infection with the parasite. This is more so because water serves as a very important component of living for humans and animals and could also serve has a vehicle of transmission of some waterborne disease organisms such as the parasite under study. It is also important to maintain surveillance of opportunistic parasites such as Cryptosporidiumin fish in the study area. This would help to create awereness in immunocompromised patients especially HIV/ AIDs patients of the need to prevent such infection which could arise from fish processing and consumption as the disease may present life threatening conplications in them. Consequently, this may serve to enlighten the general public on the need to take necessary hygienic measures when handling fish. In addition, there is paucity of information on the occurrence of Cryptosporidium in fish in Nigeria generally. Results obtained from this work in Zaria may help to establish a better understanding on the prevalence of Cryptosporidium in Clarias spp in relation to management practices by the farmers and practices of consumers.
1.4 Aim and Objectives of the Study
1.4.1 Aim of the Study
To determine the occurrence of Cryptosporidium oocystsin Clarias gariepinus and their water habitats in Zaria, Kaduna State, Nigeria
1.4.2 Objectives of the Study
The objectives of the study were to determine:
- theprevalence of Cryptosporidium in Clarias gariepinusand their habitats (water) in Zaria, Kaduna State.
- the effect of the physico-chemical parameters of the water habitats of catfishon the occurrence of Cryptosporidium in water sampled in Zaria, Kaduna State.
- the association between the prevalence of Cryptosporidium in Clarias gariepinus and sex, weight and length of catfish as well as fish management practices such frequency of pond water replacement, source of water, type of pond and method of dead catfish disposal in Zaria, Kaduna State.
1.5 Research Questions
- What is the prevalence of Cryptosporidium in Clarias gariepinus and their habitats (water), in Zaria, Kaduna State?
- Do the physico-chemical parameters of the water habitats of catfishhave any effect on the occurrenceCryptosporidium in water sampled in Zaria, Kaduna State?
- Is there anyassociation between the prevalence of Cryptosporidium in Clarias gariepinus and sex, weight and length of catfish as well as fish management practices such frequency of pond water replacement, source of water, type of pond and method of dead catfish disposal in Zaria, Kaduna State?
