M. Giles

Epidemiology of anthroponotic and zoonotic human cryptosporidiosis in England and Wales, 2004–2006

In order to monitor epidemiological trends, Cryptosporidium-positive samples (n=4509) from diarrhoeic patients were typed. Compared to the previous 4 years, the proportion of Cryptosporidium hominis cases in 2004-2006 increased to 57·3%, while 38·5% were C. parvum. The remaining 4·2% cases included mixed C. parvum and C. hominis infections, C. meleagridis, C. felis, C. ubiquitum and a novel genotype. When the typing results were combined with enhanced surveillance data to monitor risk exposures, C. hominis was linked to urban dwelling, previous diarrhoea in the household, any travel especially abroad, and using a swimming or paddling pool. C. parvum was linked to having a private water supply, contact with surface water, visiting or living on a farm, and contact with farm animal faeces. The proportion of laboratory-confirmed indigenous cases acquired from direct contact with farm animals was estimated to be 25% for C. parvum and 10% of all reported Cryptosporidium cases.

Distribution of Cryptosporidium species in sheep in the UK

There have been few studies of the distribution of Cryptosporidium species and genotypes in sheep, and the anthropozoonotic potential has been questioned since one of the major human pathogens, Cryptosporidium parvum, is not always found. To investigate the situation in the UK we undertook three studies: a reactive sampling programme of flocks identified as exposures for human cases of cryptosporidiosis; investigation of neonatal cryptosporidiosis in lambs; and a screening programme of lambs at an open farm. C. parvum was the only species found in neonatal lambs with cryptosporidiosis and predominated in flocks sampled reactively to a human case of cryptosporidiosis. C. bovis was also found in the latter study but at a lower frequency than C. parvum. C. bovis and the cervine genotype were found in the orphan lambs under the screening programme. The results of these studies show that C. parvum is important in neonatal lamb diarrhoea and is widespread in sheep flocks in the UK, but that other Cryptosporidium species and genotypes are also present. Sheep, and young lambs in particular, must still be considered as a source of C. parvum infection for humans.

DETECTION OF CRYPTOSPORIDIUM PARVUM USING A SPECIFIC POLYMERASE CHAIN REACTION

The design and use of polymerase chain reaction primers and probes as reagents for the detection of Cryptosporidium parvum are described. Sensitive and specific amplification of a 329 base pair product was demonstrated by ethidium bromide staining and hybridisation of radiolabelled probes. These reagents have the potential for application to diagnostic samples, environmental monitoring and epidemiological surveys.

Cryptosporidium hominis in a goat and a sheep in the UK.

IN THE UK, human diarrhoeal disease associated with the protozoan parasite Cryptosporidium is caused mainly by Cryptosporidium parvum and Cryptosporidium hominis , which together account for 96 per cent of cases, in approximately equal proportions ([Nichols and others 2006][1]). C parvum is

Experimental infection of a lamb with Cryptosporidium parvum genotype 1

live mites were isolated from two animals. By day 66 (44 days postchallenge) all the animals were infested with live P ovis. One ewe was seen scratching in the DJOR-29 group on day 52 of the trial. All animals were positive for live scab mites and showing clinical signs of psoroptic mange at day 72 (43 days postchallenge). All the sheep in the MOX-17, MOX-22, and MOX-29 groups remained free of signs of scab to the end of the trial on day 178. No mites were isolated from any of the sheep in the moxidectin group throughout the trial. The results of this study confirm those of previous studies showing that moxidectin has a persistent activity against P ovis of at least 28 days (Parker and others 1999). In contrast, ivermectin and doramectin did not provide protection against reinfection for the 17-day period during which P ovis can survive off the sheep. The situation regarding the DOR-17 group is worth noting, for it appears that some persistence of activity occurs. This may be marginal around the 17-day stage, being enough to prevent mite infestation in some cases and to delay the development of the disease in others. In the latter case, while still apparently free of scab, these sheep may act as sources for the spread of disease to clean flocks. The case of the ewe which lambed and, thus, was separated from the others in the group was particularly interesting, as the ewe itself appeared to have shed the infestation, but mites transferred to the lamb on which the disease then developed. The conclusion drawn from this study is that in a situation where scab mites are present, sheep injected with moxidectin may be safely reintroduced to the infected area. Conversely, when either ivermectin or doramectin are used, the animals should be moved to an uninfected area in order to avoid their reinfection from the environment.

Investigation of farms linked to human patients with cryptosporidiosis in England and Wales.

The study investigates farms suspected of being sources of zoonotic human cryptosporidiosis. A variety of implicated farm animal species were sampled and tested to detect Cryptosporidium oocysts and investigate genetic linkage with human patients. Risk factor information was collected from each farm and analysed by multivariable logistic regression to detect significant associations between factors and Cryptosporidium in animals. The results showed that average sample prevalence of Cryptosporidium infection was highest in cattle, sheep and pigs ( approximately 40-50%), in the mid-range in goats and horses (20-25%) and lowest in rabbits/guinea pigs, chickens and other birds ( approximately 4-7%). A single sample from a farm dog was also positive. Cryptosporidium parvum, which has zoonotic potential, was the commonest species and was most likely to be present in cattle and, to a lesser extent, in sheep. In particular, young calves and lambs shed C. parvum and this finding was corroborated in a statistical model which demonstrated that samples from groups of preweaned animals were 11 times, and immature animal groups six times, more likely to be positive than groups of adult animals, and that samples from a farm with a cattle enterprise were twice as likely to be positive than farms without a cattle enterprise. On seven out of eight farms, at least one C. parvum isolate from an animal sample was indistinguishable at the gp60 locus from those found in the human patients, indicating that farm animals are a likely source of infection for humans.

Cryptosporidium parvum infection in orphan lambs on a farm open to the public

A longitudinal survey was undertaken on an open farm to investigate the occurrence of Cryptosporidium species infection in orphan lambs obtained from three local flocks. During an initial pilot study, Cryptosporidium oocysts were detected by a fluorescent antibody test (fat) in the faeces of two of 21 lambs aged between one and three weeks derived from one flock (flock A). Pooled pen samples of faeces were collected weekly from lambs derived from each flock; oocysts were detected by fat in 24 (49·0 per cent) of 49 samples from lambs from flock A, 18 (30·5 per cent) of 59 samples from lambs from flock B and 14 (29·8 per cent) of 47 samples from lambs from flock C. Oocyst counts of 1 × 103 to more than 2 × 106 per gram of faeces were detected in lambs up to 12 weeks old, with the peak counts occurring at six weeks of age in the lambs from flocks A and B and at four weeks of age in those from flock C. The oocysts were confirmed by molecular analysis as Cryptosporidium parvum. Virtually all the infections were subclinical.

Prevalence and molecular typing of Cryptosporidium in dairy cattle in England and Wales and examination of potential on-farm transmission routes.

Abstract An average of 70 samples were collected from 80 dairy farms in England and Wales, from cattle, co-grazed sheep, wildlife and farm wastes, to investigate prevalence, potential sources and transmission routes of Cryptosporidium. At least one positive sample was detected on 74 of the farms (92.5%) by IFAT microscopy. The prevalence in cattle was 10.2% (95% CI 9.4–11.1%), with greater prevalences detected in calf samples, especially from those under 1 month (45.1%). Young calves were also more likely to be shedding Cryptosporidium parvum and larger concentrations of oocysts, whereas older calves and adult cattle were more likely to be shedding Cryptosporidium bovis and Cryptosporidium andersoni, respectively. The C. parvum subtypes detected were predominantly from types commonly identified in UK cattle (67% were either IIaA15G2R1 or IIaA17G1R1). A novel subtype, IIaA17G1R2, was identified from one cattle sample. The prevalence in co-grazed sheep was low (4%). Birds and rodents may represent significant reservoirs of Cryptosporidium due to high prevalence, large oocyst concentrations, and the detection of a C. parvum subtype known to be present in human populations, identified in samples from these wildlife. Cryptosporidium were detected in dirty water and manure, and also from pasture samples where slurry had been spread. On 64% of the farms, identical Cryptosporidium species were detected (mainly C. parvum or C. bovis) from different cattle groups on the farms, although no direct or indirect contact between the groups were recorded, apart from sharing staff. The same Cryptosporidium species were found in cattle, farm wastes and bird samples on the same farms, but rarely, or not at all, present in sheep or rodent samples. The matching of species/subtypes was also related to the proximity of the different sample sources which may indicate a potential transmission route.

Investigation of the role of companion animals in the zoonotic transmission of cryptosporidiosis.

Companion animals owned by human patients with cryptosporidiosis (cases) and those animals owned by the wider human population (controls), were studied to determine whether Cryptosporidium was more likely to be excreted by case animals than controls. A total of 280 recently voided faecal samples (114 case animals and 166 control animals) were collected and tested by immunomagnetic separation and immunofluorescent microscopy. A multivariable model was also created to identify pet characteristics, contacts and management factors associated with Cryptosporidium infection in animals, using information collected by a standardized questionnaire. The model was designed to take into account the clustering of samples at the owner level and whether the sampled animal was a case or control.

Cryptosporidium species in lambs submitted for diagnostic postmortem examination in England and Wales

CRYPTOSPORIDIOSIS is a common enteric disease in human beings and a wide range of animal species. Cryptosporidium parvum is the main species responsible for zoonotic infection in Britain. In a previous study, [Pritchard and others (2007)][1] evaluated the zoonotic hazard associated with subclinical