T. de Waal

The comparative efficacy of four anthelmintics against a natural acquired Fasciola hepatica infection in hill sheep flock in the west of Ireland.

The aim of this study was to evaluate the efficacy of four different anthelmintics against F. hepatica in a naturally infected hill sheep flock in the west of Ireland. In a randomised trial, 138 ewes were divided into four groups. On day 0 each group was dosed with one of four anthelmintics: triclabendazole, closantel, oxyclozanide or nitroxynil. Faecal samples were obtained from each animal per rectum on the day of treatment and again at 7, 14, 21 and 56 days post-treatment. The number of F. hepatica eggs per gram of faeces was determined using the sedimentation technique and the efficacy of each anthelmintic was calculated in terms of the percentage reduction in egg count at each time point. The results for closantel, oxyclozanide and nitroxynil indicate that these drugs are effective with faecal egg count being reduced by 100% by day 14 post-treatment. However, the results for triclabendazole group yielded lower efficacy levels, with faecal egg count reductions of between 49% and 66% based on arithmetic means, over the period 7-56 days post-treatment. These results are highly indicative of triclabendazole resistant F. hepatica in sheep on this farm.

Prevalence of Cryptosporidium species in intensively farmed pigs in Ireland

Natural Cryptosporidium infections in pigs are widespread but generally apathogenic. This study was undertaken to determine the prevalence of zoonotic Cryptosporidium spp. in piggeries in Ireland, where the drinking water supply is particularly vulnerable to contamination with zoonotic species. Overall, infections were detected in 39 out of 342 animals (11.4%), with highest infection rates among weaners (15%) and sows (13.3%). Twenty-nine positive samples were genotyped based on SSU rRNA sequence analysis. Infections with Cryptosporidium parvum, the most important zoonotic species were rare and are likely to be of greater concern to animal handlers than suppliers of drinking water. In addition to C. parvum, Cryptosporidium suis, Cryptosporidium pig genotype II, Cryptosporidium muris and a previously undescribed genotype were identified. ABI-profiles indicated the presence of different alleles in at least 40% of all genotyped isolates. This was confirmed in 3 isolates by cloning of the PCR products. Since chronic mixed infections appear to be quite common in pigs they could be considered as models for mixed infections in immunocompromised humans.

Advances in diagnosis of protozoan diseases.

Microscopy still remains the gold standard procedure for the diagnosis of many protozoan infections in animals, but the specific identification requires skilled and experienced personnel. Immunoassays, detecting antibodies or specific protozoan antigens, have been developed but often lack sensitivity and specificity due to close relationship between many protozoa. Recent research has focussed almost exclusively on molecular based techniques for the identification and quantification of parasite DNA in samples. Opinion differ on most appropriate targets to use and there are very few diagnostic kits available making comparison between laboratories difficult. Future research needs to focus on robust, cheap field diagnostic assays.

Weather and soil type affect incidence of fasciolosis in dairy cow herds

Fasciolosis caused by Fasciola hepatica is generally a subclinical infection of dairy cows and can result in marked economic losses on Irish dairy farms. This study investigated the exposure to F hepatica in 237 dairy cow herds, using an in-house antibody-detection ELISA applied to bulk tank milk (BTM) samples collected in the autumn of 2012. A total of 364 BTM samples were collected from 237 different herds, with 127 farmers submitting BTM samples in two consecutive months. Analysis of the BTM samples indicated that 67 per cent (n= 159) of the dairy herds had been exposed to F hepatica. Rainfall, temperature and soil types were significantly different between the exposed and non-exposed herds (P<0.05), highlighting the role of these variables to the exposure to F hepatica. Among the 127 herds that provided two monthly milk samples, 83 herds were exposed to F hepatica and 82 increased their F hepatica antibody levels at the later sampling time (P<0.01).The findings of this study confirm the high prevalence of F hepatica antibodies in Irish dairy herds and show the rise in antibody levels during autumn. This study is the first step towards assessing the spatiotemporal pattern of fasciolosis in dairy herds in Ireland.

Toxoplasma gondii in Ireland: seroprevalence and novel molecular detection method in sheep, pigs, deer and chickens.

Toxoplasma gondii is among the most studied parasites worldwide but there is not much information about it published in Ireland. The objectives of this study were to determine the seroprevalence of T. gondii in sheep, pigs, deer and chickens and the molecular detection of T. gondii DNA in muscle tissue. Serum samples were collected from these species at the time of slaughter at Irish abattoirs during 2007 and tested for anti‐T. gondii antibodies using a commercial semi‐quantitative latex agglutination test. Antibodies (titre ≥1 : 64) were found in 36% (105/292) sheep, 4.7% (15/317) pigs and 6.6% (23/348) deer. In chickens, 18% (65/364) had antibody titres, ranging between 1 : 5 and 1 : 1024. Significant (P ≤ 0.05) age‐related differences in seroprevalence were found in adult sheep (58.1%) and pigs (23.1%). Significant gender differences in seroprevalence was also found in sheep with more females (43%) than males (22.4%) being positive. However, when adjusted for age through logistic regression gender was no longer significant. Seroprevalence was also evaluated on farm locations grouped to NUTS level 3, but the prevalence was too low to draw any statistical conclusions. Using a nested PCR, the presence of T. gondii DNA was detected in diaphragm samples from 3.6% (3/83) sheep, 13.0% (3/23) pig and 4.2% (3/71) deer. Meat digestion liquids from a Trichinella spp. survey in pigs were also used for the first time to detect T. gondii. Toxoplasma gondii DNA was detected in 50% (10/20) of pooled samples. This is the first in depth study of T. gondii seroprevalence in animals in Ireland and a novel method, using digestion liquid from pooled diaphragm samples, for PCR detection in pigs is described.

Longitudinal and spatial distribution of GP60 subtypes in human cryptosporidiosis cases in Ireland

Within Europe, Ireland has one of the highest reported infection rates with the diarrhoeal protozoan pathogen Cryptosporidium. In this study 249 Cryptosporidium parvum isolates collected from Irish patients between 2000 and 2009 were subtyped by sequence analysis of the GP60 locus. A subsample of 127 isolates was also typed at the MS1 and ML1 loci. GP60 subtype IIaA18G3R1 was the predominant subtype in every year and every season throughout the country. Over the 10-year period there was no evidence that host immunity to the predominant subtype caused a shift in its prevalence. Length frequency distributions of the GP60 TCA/TCG repeats compiled from published data, showed distinct patterns for countries with predominantly zoonotic or anthroponotic transmission cycles, respectively. Although considered to be mostly affected by zoonotic cryptosporidiosis, the GP60 fragment length of Irish C. parvum isolates mirrored that of countries with predominantly human-to-human transmission, indicating more complex routes of infection between livestock and humans. Due to their homogeneity, ML1 and MS1 were not considered useful loci for subtyping C. parvum strains in Ireland.

Bovine besnoitiosis (Besnoitia besnoiti) in an Irish dairy herd

Bovine besnoitiosis, caused by the apicomplexan protozoan parasite Besnoitia besnoiti, was diagnosed in an Irish dairy herd. This is the first diagnosis of besnoitiosis in Ireland or the UK and the most northerly European outbreak yet described. The diagnosis occurred following a farm investigation in June 2015 into an unusual dermatological problem that had been ongoing since 2010. On an annual basis, 1–2 per cent of cows in the herd exhibited clinical signs, including skin thickening, alopecia, weight loss and poor performance. Others displayed pyrexia, limb oedema, respiratory distress and reduced milk yield. Histopathological examination of skin revealed granulomatous and eosinophilic dermatitis, with characteristic intradermal protozoal cysts, consistent with cutaneous besnoitiosis. Follow-up serological testing and clinical examination of cattle (n=228) on the farm found that 68 per cent (144/212) were seropositive for B. besnoiti. In addition, 51 per cent (117/228) had characteristic scleral conjunctival cysts and 68 per cent (134/198) had vulval cysts. Postmortem examination of a severely affected animal revealed typical gross and histopathological lesions of B. besnoiti infection. These results confirmed endemic infection with B. besnoiti. The identification of this exotic disease highlights the importance of veterinary surveillance at both local and national level, particularly in relation to emerging diseases.

Controlling nematodes in dairy calves using targeted selective treatments

With increasing concerns of anthelmintic resistance in cattle nematode populations worldwide, there is a need to explore alternative approaches to nematode control. One alternative approach is the use of targeted selective treatments (TST) where only individual animals are treated instead of the entire group. This study reports the findings of a TST approach in dairy calves conducted over their first grazing season (FGS) to control both gastrointestinal nematode and lungworm challenge. Ninety-six calves with an initial mean (s.d.) age and live weight of 130 (28.3) days and 120 (23.6)kg, respectively, were randomised by breed, age and live weight to one of two treatments; Control (n=24; ×2) and TST (n=24; ×2). Control calves were treated three times at pasture with ivermectin by subcutaneous injection. Individual calves in the TST group were treated at pasture with ivermectin when one of the following thresholds was met: (1) positive for lungworm larvae using the modified Baermann technique or (2) positive or negative for lungworm larvae using the modified Baermann technique with plasma pepsinogen concentration (PP) ≥ two international units of tyrosine/litre and faecal egg count (FEC) ≥ 200 strongyle eggs per gram of faeces. Calves were rotationally grazed from July 3rd 2012 (day 0) to November 2nd 2012 (day 122) when calves were housed. Calves were weighed and sampled (blood and faecal) every three weeks. There was an effect of treatment and time on both FEC [treatment (P=0.023), time (P<0.001)] and PP [treatment (P=0.002), time (P<0.001)]. Both FEC and PP were higher in TST calves. There was a 50% reduction in anthelmintic use in TST calves compared to control calves. Clinical signs of lungworm infection, confirmed by the modified Baermann technique, were evident in TST calves on days 62 and 63 of the study. The average daily live weight gain for control and TST calves was 0.50 (0.02)kg day(-1) and 0.47 (0.03)kg day(-1), respectively (P=0.41). Thus, performance in dairy calves can potentially be maintained with fewer anthelmintic treatments but farmers need to be vigilant of the challenge posed by lungworm. Any future approach into the use of TST in FGS calves must take into consideration the relative importance of lungworm as a pathogen.

Detection of anthelmintic resistance on two Irish beef research farms.

Beef and milk production systems in Ireland are largely dependent on a grass-based diet with cattle spending long periods of the year at pasture (Drennan and McGee 2009). As a result, cattle are frequently exposed to gastrointestinal nematode (GIN) challenge. Within grass-based production systems, anthelmintics are essential to optimising performance and any reduction in their efficacy may lead to reduced animal performance. Although anthelmintic resistance (AR) is more commonly reported in sheep (Sutherland and Leathwick 2011), it has been increasingly reported in cattle worldwide (Stafford and Coles 1999, Loveridge and others 2003, Soutello and others 2007, Demeler and others 2009, Edmonds and others 2010). To date, there have been no published reports of AR in cattle in Ireland. We report the findings of a faecal egg count reduction test (FECRT) conducted at two Irish agricultural research farms (Study A and B). Two different software programmes were used to determine anthelmintic efficacy. All animal procedures performed in this study were conducted under experimental license (B100/2869) from the Irish Department of Health and Children, in accordance with the Cruelty to Animals Act 1876 and the European Communities (Amendment of Cruelty to Animals Act 1876) Regulation 2002 and 2005. Study A was conducted at Teagasc, Johnstown Castle, Wexford, Co. Wexford, Ireland (longitude 6°30′ W; latitude 52°17′ N; …

Comparison of three methods for the detection of Angiostrongylus vasorum in the final host

Angiostrongylosis is potentially fatal parasitic nematode infection affecting dogs which can be difficult to diagnose. In recent years several microscopical, serological and molecular detection methods have been developed, however there are few studies that have compared the relative performance of these methods. Screening necropsy material from an opportunistic sample of 140 foxes (82 of which were considered to be infected with Angiostrongylus vasorum), indicated sensitivities of 84.1% for dissection and visual examination of plucks, 69.5% for nested PCR of an 18S rRNA fragment and 76.8% for a canine A. vasorum antigen detection test (IDEXX Angio Detect) of tissue fluid samples respectively. Agreement between the tests ranged from 45.6 to 79.7%. A novel nested PCR-RFLP for the detection and identification of canid lungworm spp. is described.