Gary Conboy

Increase in milk yield following eprinomectin treatment at calving in pastured dairy cattle

Gastrointestinal nematodes rarely cause signs of clinical disease in adult cattle. However, they have been shown to exert a negative impact on production in lactating animals, as seen by improved production following elimination of the worms using anthelmintics. A double blind, randomized clinical trial was performed in 28 dairy herds in Canada. The objective of the study was to evaluate the effect of treatment with eprinomectin pour-on solution (IVOMEC EPRINEX) at calving on production, in cattle that have had some exposure to pasture. Cows were randomly allocated to treatment or placebo in blocks of 10, based on calving date, and treated with eprinomectin or placebo on the day of calving. Information on milk production was obtained from all animals, as well as recorded cases of selected diseases. Milk production results from the Canadian dairy herd management system database were analysed using a mixed model with herd as a random effect and test within-cow as a repeated measurement. Test day milk yields from the first six tests after treatment were included in the model, representing a period of between 180 and 200 days in milk (dim). Treated cows produced an additional 0.94 kg of milk per day when compared to the controls over this period. The production effect was independent of calving season, age of the animal and geographical location. No effect of treatment was seen on milk composition, somatic cell count (scc) or on the selected health parameters that were recorded for all included animals. Monthly fecal egg counts (FEC) were performed for eight randomly selected animals in each herd. The observed FEC were low in this study, with a range from 0 to 419 trichostrongyle type eggs per 5g (ep5g) of feces in animals not yet treated with the anthelmintic. The average count was 9.8 and the median was 1.0. FECs dropped immediately after calving and stayed lower for at least 100 days in treated animals when compared to controls. In conclusion, gastrointestinal nematodes appear to have an effect on milk production in Canadian dairy cows that have had some degree of pasture exposure. Eliminating the present subclinical parasite burdens produced a consistent increase in milk production that can yield economic benefits for the dairy producer.

Pathological Findings in Dogs Naturally Infected with Angiostrongylus Vasorum in Newfoundland and Labrador, Canada

Fifty-six dogs from St. Johns, Newfoundland, Canada, were evaluated for Angiostrongylus vasorum infection. Small numbers of nematodes were found within pulmonary arteries of 6 dogs. Larvae were identified in fecal samples in 2 of 6 dogs. All 6 dogs had multifocal granulomatous pneumonia and sometimes foci of chronic thrombosis, which varied from very mild to severe. One dog had extensive pulmonary lesions resulting in cor pulmonale. Right heart failure was characterized by right ventricular hypertrophy, hepatic congestion, ascites, and hydrothorax. Microscopically, in most cases, eggs, larvae, and sometimes intravascular adults, were present within lung tissue sections. Small foci of granulomatous inflammation with and without larvae were present in kidney and brain in 4 dogs. An additional dog, diagnosed antemortem with angiostrongylosis via fecal examination, was also examined. Pathological findings consisted of severe pyogranulomatous interstitial pneumonia with myriad eggs, larvae, and numerous intravascular pulmonary adult nematodes with extensive arterial thrombosis. Five hundred and seventy-two adult worms were removed from pulmonary arteries. Foci of granulomatous inflammation, often associated with larvae and/or eggs, were present in tracheobronchial lymph nodes, adrenal gland, brain, and kidneys. Severe seizuring noted antemortem was attributed to several large, discrete areas of acute hemorrhagic infarction within the cerebrum and cerebellum. Natural A. vasorum infection in domestic dogs in eastern Newfoundland causes lung pathology of variable severity, which in some cases, may progress to cor pulmonale and which may be associated with extrapulmonary lesions and clinical signs.

Canine angiostrongylosis: the French heartworm: an emerging threat in North America.

Angiostrongylus vasorum, French heartworm, is a metastrongloid parasite found in the pulmonary arteries and right ventricle of wild and domestic canids and various other animals. The natural definitive hosts are species of foxes. The geographic distribution of the parasite includes various countries of Europe, Africa, South America, and North America. Angiostrongylosis is considered an emerging disease in dogs in Europe. In North America, autochthonous A. vasorum infection occurs only in the Canadian province of Newfoundland-Labrador. Computer modeling suggests there is a high probability that A. vasorum will spread to other parts of North America and will likely become endemic in the eastern half of the continent and in the states and provinces along the western coast. Animals acquire infection by the ingestion of gastropod or frog intermediate hosts that carry the infective 3rd-stage larvae. Frogs can also serve as paratenic hosts. Definitive antemortem diagnosis is by detection of L(1) in feces, sputum, or bronchoalveolar lavage samples. Baermann fecal examination is the most reliable method for fecal detection. However, false negative results can occur due to the typical erratic/sporadic fecal larval shedding pattern of A. vasorum. Recently, promising new methods for A. vasorum infection diagnosis have been reported involving polymerase chain reaction of blood and fecal samples and a sandwich ELISA for detection of circulating worm excretory/secretory antigen. Current treatment options include moxidectin, milbemycin oxime, and fenbendazole.

Relationships between bulk-tank antibodies to Ostertagia ostertagi and herd-management practices and measures of milk production in Nova Scotia dairy herds

Monthly bulk-tank milk samples were obtained from 415 Nova Scotia dairy herds in each of the months of July-September 1998 and tested using an indirect microtitre ELISA against a crude saline-extract, whole-worm Ostertagia ostertagi antigen. ELISA results (optical densities (ODs)) were consistent across months (r=0.85) but there was considerable variation among herds. A questionnaire was sent by mail to all producers; information on management factors that would potentially influence parasite burdens in the herds was obtained from 239 farms. Data on annual milk production, summer milk production (July-September) and seasonal decline in milk production were obtained from the Animal Productivity and Health Information Network (APHIN) database. Associations between management practices and ODs, and between ODs and milk-production parameters were studied. Some management practices known to be associated with parasite burdens had expected directions of association with the ODs, giving supporting evidence that the ELISA is a reasonable measure of parasite burden. Most notably, ODs were increased with greater exposure of heifers or milking cows to pasture. ODs were not associated with either annual milk production or seasonal decline in milk production. However, there was a substantial relationship between the herd OD value and the level of milk production during the summer. An increase in the OD from 0.58 to 0.83 (the interquartile range of ODs) was associated with a reduction in production of 1.25kg/cow/day.

Zoonotic potential of Giardia duodenalis and Cryptosporidium spp. and prevalence of intestinal parasites in young dogs from different populations on Prince Edward Island, Canada

The prevalence of Giardia duodenalis, Cryptosporidium spp. and other intestinal parasites was determined in dogs <1 year old from Prince Edward Island, Canada. Fecal samples were collected from the local animal shelter (n=62), private veterinary clinics (n=78) and a pet store (n=69). Intestinal parasites isolated included G. duodenalis, Cryptosporidium spp., Toxocara canis, Isospora spp. and Uncinaria stenocephala. To estimate the zoonotic risk associated with these infections, genotypes of G. duodenalis and Cryptosporidium spp. were determined using 16S rRNA and Hsp70 gene sequencing, respectively. Dogs from the pet store had the highest prevalence of intestinal parasites (78%, 95% CI: 68-88%), followed by the private veterinary clinics (49%, 95% CI: 37-60%), and the local animal shelter (34%, 95% CI: 22-46%). The majority G. duodenalis belonged to host-adapted assemblages D (47%, 95% CI: 31-64%) and C (26%, 95% CI: 13-43%), respectively. Zoonotic assemblages A and B were isolated alone or in mixed infections from 16% (95% CI: 6-31%) of G. duodenalis-positive dogs. All Cryptosporidium spp. were the host-adapted C. canis. While host-adapted, non-zoonotic G. duodenalis genotypes were more common, the presence of G. duodenalis assemblages A and B, T. canis, and U. stenocephala suggests that these dogs may present a zoonotic risk. The zoonotic risk from Cryptosporidium-infected dogs was minimal.

Distribution of Crenosoma Vulpis and Eucoleus Aerophilus in the Lung of Free-Ranging Red Foxes (Vulpes Vulpes):

Crenosoma vulpis and Eucoleus aerophilus are nematode parasites that can cause verminous pneumonia in wild carnivores. There is a paucity of information regarding the distribution of parasites in the lungs and the relationship between histopathological and parasitological diagnoses in naturally infected foxes. The objectives of this study were: first, to study the lobar and airway distribution of C. vulpis and E. aerophilus in wild red foxes and second, to investigate the relationship between fecal and histopathological diagnoses. Samples from 6 sites of the lung and fecal contents were obtained from 51 wild foxes in Prince Edward Island. By fecal examination, 78.4% of wild foxes tested positive for C. vulpis and 68.6% for E. aerophilus. In contrast, 66.6% and 49% of foxes had histopathological evidence of C. vulpis and E. aerophilus in the lungs, respectively. Anatomically, C. vulpis was observed in the small bronchi and bronchioles of all pulmonary lobes whereas E. aerophilus was restricted to the large bronchi and the caudal lobes. Affected airways exhibited severe epithelial glandular hyperplasia and bronchiolar mucous metaplasia. It was concluded that C. vulpis is widely distributed in airways of all pulmonary lobes, whereas E. aerophilus is mainly restricted to the bronchi of caudal lobes. Also, this study showed that histological examination of lung underestimates the infection with E. aerophilus.

Effects of farm management practices and environmental factors on bulk tank milk antibodies against gastrointestinal nematodes in dairy farms across Canada

Enzyme-linked immunosorbent assays (ELISAs) have been used as a diagnostic tool to quantify levels of gastrointestinal nematodes in dairy cattle by measuring Ostertagia ostertagi antibodies in milk. Higher levels of O. ostertagi antibodies measured by ELISA methods, referred to as optical density ratios (ODRs), are associated with decreased milk production in dairy cattle. On-farm management practices (e.g. pasturing techniques and anthelmintic usage) can influence the exposure of cattle to nematode infections and the magnitude of acquired worm burdens. Additionally, environmental and climatic factors, such as land elevation and precipitation, may also influence the levels of gastrointestinal parasitism. This repeated cross-sectional study investigated the effect of farm management practices and surrounding environmental factors on bulk tank (BT) ODRs in herds from provinces across Canada, and further examined the potential effects of various anthelmintic treatment protocols on BT ODRs. A total of 195 herds contributed an average of 3.5 BT samples between December 2003 and April 2005. The farm management practices were recorded from a questionnaire asking producers about their pasturing methods (confined, pastured, etc.), pasture sharing practices (e.g. mixing heifers with milking cows) and anthelmintic treatments. Environmental data were downloaded online from various governmental databases (e.g. Natural Resources Canada, Statistics Canada, Environment Canada, etc.). Statistical models, accounting for repeated measures (multiple BT ODRs for each farm) and for clustering of farms within a region (province or ecoregion), were used to analyze environmental and farm management data. Overall, the greater the exposure that heifers and milking cows had to pasture, the higher the levels of anti-parasite antibodies detected in BT samples. Treating the entire herd or treating milking cows at calving reduced BT ODR values. Farms in areas with higher number of rainy days, higher normalized difference vegetation index (NDVI) values, and lower land surface temperatures (LSTs), were also likely to have higher BT ODRs. Seasonal variation was such that late summer and early fall, when parasite load was at its highest, yielded larger BT ODRs. Due to the high clustering effect at the herd level, factors at the herd level (e.g. pasturing methods, anthelmintic administration) had a higher potential impact on bulk-tank measurements than the herds surrounding environmental factors.

Efficacy of a Single Topical Application of Advantage Multi® (= Advocate®) Topical Solution (10% Imidocloprid + 2.5% Moxidectin) in the Treatment of Dogs Experimentally Infected with Crenosoma vulpis

Crenosoma vulpis is a metastrongylid lungworm of canids causing chronic respiratory disease in dogs in parts of North America and Europe. The objective of this study was to determine the efficacy of imidacloprid 10% + moxidectin 2.5% (Advantage Multi®/Advocate® Topical Solution) against C. vulpis infection in experimentally infected dogs. Eighteen beagles (9 M, 9 F) were each given 100 infective third-stage larvae of C. vulpis. The 16 dogs (8 M, 8 F) with the highest faecal larval counts were stratified by gender and larval counts and randomly assigned to a treatment group. Group 1 received placebo only; group 2 was given a single topical treatment of Advantage Multi®/Advocate® (10 mg/kg imidacloprid/2.5 mg/kg moxidectin) at 4 weeks PI. Dogs were euthanised at 8 weeks PI and the lungs were removed and examined for the presence of adult worms by lung flush. The mean (geometric) number for adult C. vulpis recovered in untreated dogs was 70.0 (range 58 to 87) compared with 0.0 in animals treated with Advantage Multi®/Advocate®. The resulting efficacy against C. vulpis was 100%. The number of C. vulpis was significantly lower for treated dogs than the burden shown in the untreated group (p = 0.003).

Efficacy of Milbemax (milbemycin oxime + praziquantel) in the treatment of dogs experimentally infected with Crenosoma vulpis

Crenosoma vulpis, the fox lungworm, infects wild and domestic canids and is a cause of chronic respiratory disease in dogs in North America and Europe. The objective of this study was to determine the efficacy of milbemycin oxime (0.5mg/kg)/praziquantel (5mg/kg) (Milbemax; Novartis Animal Health, Inc.) against C. vulpis infection in a randomized, blinded, placebo-controlled study using experimentally infected dogs. Sixteen beagles (8 males, 8 females) were each given 100 infective third-stage larvae of C. vulpis. Fecal samples were examined for first-stage larvae by quantitative Baermann examination pre-exposure and at days 21, 28, 35, 42 and 49 post-infection (PI). All of the dogs were shedding larvae in the feces at 21 days PI. The dogs were randomly assigned to one of two groups. At 28 days PI, Group 1 (4 males, 4 females) received placebo only while Group 2 (4 males, 4 females) received a single treatment of milbemycin oxime (0.5mg/kg) and praziquantel (5mg/kg). The 16 dogs were euthanized and necropsied at 49 days PI. Lungs were removed, assessed for gross lesions (graded on a subjective scale 0-3 with 0 being normal) and C. vulpis were collected by lung-flush and counted. Samples of lung tissue were preserved for evaluation of histopathology and the lesions graded on a subjective scale (0-3 with 0 being normal). Gross and histopathology lesions were detected in all 8 untreated Group 1 dogs with mean subjective lesion scores of 1.8 ± 0.7 (range 1-3) and 3.0 ± 0.0 (range 3), respectively. Gross lesions were observed in 3/8 and histopathology lesions in all 8 of the treated Group 2 dogs with mean subjective lesion scores of 0.4 ± 0.5 (range 0-1) and 1.3 ± 0.4 (range 1-2), respectively. The mean (geometric) number for adult C. vulpis recovered in untreated dogs was 48.3 (range 25-70) compared with 0.65 (range 0-2) in animals treated with Milbemax. The resulting efficacy against C. vulpis was 98.7%. The number of C. vulpis was significantly lower for treated dogs than the burden in the untreated group (p=0.0002). A single dose of Milbemax (milbemycin oxime 0.5mg/kg+praziquantel 5mg/kg) was highly effective for the treatment of patent C. vulpis infection in dogs. A dosing interval for the prevention of clinical disease in dogs exposed to natural infections has not been established.

Comparison of five diagnostic tests for Giardia duodenalis in fecal samples from young dogs

Five diagnostic tests were compared for the diagnosis of Giardia duodenalis in fecal samples of young dogs. Fecal samples were collected from 136 healthy dogs <1year old and examined using immunofluorescence antibody microscopy (IFA) after sucrose gradient centrifugation, zinc sulfate centrifugal flotation technique (ZSCT), SNAP®Giardia test, and ProSpecT®Giardia EZ Microplate assay. In addition, polymerase chain reaction (PCR) of the 16S rRNA gene was performed. Kappa (κ) statistic was calculated to assess diagnostic agreement between the IFA and each test. Using the IFA as the gold standard, the relative sensitivity and specificity of each test were determined. Subsequently, a Bayesian approach was used to estimate the sensitivity and specificity of each test in comparison to the IFA results. Giardia duodenalis was detected in 41% of the samples examined by IFA. The ZSCT resulted in 37% of positive samples, with a relative sensitivity and specificity of 86 and 98%, respectively. The SNAP®Giardia test was positive in 40% of the samples, with a relative sensitivity and specificity of 91 and 96%, respectively. The ProSpecT® test was positive in 51% of the samples, with a relative sensitivity and specificity of 100 and 83%, respectively. The relative sensitivity and specificity for PCR were 58 and 56%, respectively, with 55% of samples being PCR-positive. While the sensitivity and specificity estimates of each test in comparison to the IFA changed when using a Bayesian approach, the conclusions remained the same. While the ProSpecT® test was the most sensitive test in this study, it is not designed for dogs and more costly than the other tests. The SNAP®Giardia test performed similar to the ZSCT but may be more favorable because it is fast and easy to perform. Performance of the PCR was poor and the benefit of PCR may be in determining genotypes for evaluating zoonotic transfer between dogs and humans.