Prevalence, Characterization and Transmission of Cryptosporidium species between animals and Humans on Diary Farms in Zambia
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Date
2012-09-17
Authors
Siwila, Joyce
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Abstract
In the last two decades, Cryptosporidium infection has increasingly become important as a cause of diarrhoea in humans especially in children under the age of 5 years and in the immuno-compromised, particularly those with Human Immunodeficient Virus or acquired immunodeficiency syndrome (HIV/AIDS). This is especially so in developing countries such as Zambia where there is high HIV/AIDS prevalence, which is currently estimated to be 16% among adults of reproductive age.
There are, however, no known reports in Zambia of whether farm workers who are constantly in touch with animals are at risk of getting Cryptosporidium infection directly from these animals and information on genotypes involved is also lacking. The absence of such important information led to the formulation of this study. The aims of this study were to determine the presence of Cryptosporidium infection in dairy calves and in lambs and goat kids on selected dairy farms on one hand and in humans working with animals and members of their households on the other hand, using a copro-antigen enzyme linked immunosorbent assay (ELISA). Management factors and potential risk factors of infection were also investigated through questionnaires to find out if there was any possible association with the occurrence of Cryptosporidium infection in animals and humans. Genotypes of parasites isolated were also determined.
The faecal samples were collected per rectum from 207 calves, 39 lambs and 14 kids, aged six weeks and below belonging to 20 dairy farms in Lusaka and Central provinces between October 2004 to March 2005. Stool samples were also collected from 289 humans of various ages ranging from 0 to 60 years after informed consent. The faecal consistency was noted for each sample after which the samples were frozen until analyzed.
The copro-antigen ELISA analysis showed an overall Cryptosporidium prevalence of 33.8% in calves. When the farms were divided into large-scale and small-scale dairy farms based on the total number of animals reared on the farm, the prevalence was found to be 39.02% for the large-scale farms and 13.95% for the small-scale farms. The prevalence in lambs was 2.6% while that for the kids was 7.1%.Out of the 289 human stool samples from 89 families that were analyzed, 6.2% were positive for Cryptosporidium. Ten (5.7%) of these were males while 8 (7.2%) were females. Eight of the positive males were farm workers while two were non-farm workers. All the positive females were non-farmnvorkers. The highest number of positive individuals was in the age range of 21-30 years. The positive humans were from eight farms only out of the 20 farms sampled.
Results from the questionnaire survey on calf management factors and their association with infection with Cryptosporidium, indicated a significant difference in prevalence between individually housed calves and those that were housed in groups (X^=33.420, P<0.0001). The prevalence was higher in individually housed calves (52.4%) as compared to those housed in a group (16.3%). The frequency of bedding removal was also significantly associated with the prevalence of cryptosporidial infection (^^=38.875, P<0.0001). Bottle/bucket feeding was also associated with the infection (x^= 13.034, P=0.04) as opposed to suckling. Cryptosporidium infection was also significantly associated with faecal consistency, with prevalence of 51.4%, 38.6% and 10% for normal, watery and pasty faeces, respectively (x^=9.228, P=0.010).Questionnaires were administered to 89 households to determine if contact with animals, occurrence of diarrhoea in the home, water source and sharing water source with animals were associated with cryptosporidial infections in farm workers and their families. The individuals that had contact with neonatal calves were 2.091 times more likely to be infected with C. parvum than those that did not have contact. Those that had diarrhoea in the home were also 2.295 times more likely to have the infection but the association in both cases was not significant. Age was also not significantly associated with Cryptosporidium infection (x^=8.825, /'=0.184).Twenty positive calf samples, one lamb and one kid samples were analyzed using Polymerase Chain Reaction (PCR). Amplification products using the Heat Stock Protein (HSP-70) gene and the 18S rDNA gene were obtained for 20 isolates from calves and for the lamb and kid samples. After sequence analysis, Cryptosporidium parvum bovine genotype, C bovis and a deer-like genotype were identified from calf isolates.'The lamb sample revealed C. parvum bovine genotype while the kid sample revealed C. suis.Amplification products for the HSP-70 gene and 18S rDNA gene were also obtained for nine and 14 human samples, respectively. Four samples did not amplify on both the 18S rDNA gene and the HSP-70 gene. Sequence analysis on the amplified samples revealed C. parvum bovine genotype and C. hominis. These genotypes were found in both the fann workers and non-farm workers.
From this study, it can be concluded that Cryptosporidium infections are prevalent in Zambian dairy cattle, sheep and goats. It can also be concluded that Cryptosporidium infection is prevalent in humans working and living on dairy farms. The C. parvum bovine genotype was found in humans, an indication that humans are at risk of infection and do get infected with the animal type of Cryptosporidium parasites. However, the strength of association between the potential risk factors and the occurrence of cryptosporidiosis could not be conclusively established. In view of this, it is, therefore, recommended that fiarther studies be done to include other areas of the country and further genotyping of Cryptosporidium isolates from humans also be expa
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Keywords
Cryptosporidiosis---Zambia , Coccidiosis in Animals