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.

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.

Serologic detection of Angiostrongylus vasorum infection in dogs.

Angiostrongylus vasorum, French Heartworm, is a metastrongylid nematode infecting the pulmonary arteries and right heart of wild and domestic canids in various regions of the world. Infection in dogs can result in fatal cardiopulmonary disease. A single endemic focus of A. vasorum in North America occurs in the southeastern portion of Newfoundland, Canada. Dogs are currently diagnosed by detection of first-stage larvae shed in feces using the Baermann technique or fecal flotation. However, these procedures may lack sensitivity due to intermittent fecal larval shedding. The potential for using detection of circulating worm antigen for diagnosis was investigated by developing a sandwich-ELISA using rabbit anti-whole adult worm antiserum. This test detected circulating antigen in sera from 22/24 Baermann positive dogs naturally infected with A. vasorum. Negative results (0/52) were obtained from sera collected from Baermann negative dogs from outside of the endemic region, and from sera (0/30) from dogs from non-endemic regions that were infected with Crenosoma vulpis, the fox lung worm. Receiver operating curve analysis gave a specificity of 100% and a sensitivity of 92% for the sandwich-ELISA at an optical density cut-off of 0.19. Subsequently, 239 dogs from Newfoundland displaying clinical signs of cardiopulmonary disease, were examined using both the Baermann fecal examination and the sandwich-ELISA. Larvae were detected in 10% (24/239) of these dogs by fecal examination, whereas the sandwich-ELISA detected circulating antigen of A. vasorum in serum from 18.8% (45/239) of the dogs. This suggests that fecal diagnostics may have missed approximately half of the A. vasorum infected dogs, and that the sandwich-ELISA may be a useful tool in the diagnosis of this parasite.

Natural infections of Crenosoma vulpis and Angiostrongylus vasorum in dogs in Atlantic Canada and their treatment with milbemycin oxime.

Milbemycin oxime was used to treat dogs with natural infections of the fox lungworm, Crenosoma vulpis and the French heartworm, Angiostrongylus vasorum. Crenosomosis was identified in 42 of 202 dogs with clinical signs of coughing, dyspnoea or exercise intolerance by a Baermann analysis of faecal samples taken between October 2000 and October 2001. It occurred throughout Atlantic Canada (New Brunswick, Newfoundland, Nova Scotia and Prince Edward Island). The clinical signs resolved and shedding of larvae in faeces ceased in all 32 Crenosoma-infected dogs given a single oral dose of 0.5 mg/kg milbemycin oxime for which the results of faecal examinations were available. Angiostrongylosis was identified in 16 of the 202 dogs and was restricted to the Avalon peninsula of Newfoundland, where 67 dogs were tested. The clinical signs resolved and shedding of larvae ceased in 14 of the 16 dogs treated with four, weekly oral doses of 0.5 mg/kg milbemycin oxime. One dog with severe clinical signs died during the course of treatment and one owner failed to provide a faecal sample from their dog but reported that the clinical signs had resolved.

Evaluation of the repeatability of a crude adult indirect Ostertagia ostertagi ELISA and methods of expressing test results.

An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against Ostertagia ostertagi using a crude adult worm antigen was evaluated using serum and milk samples from adult cows, as well as from bulk tank milk. Within and between plate repeatabilities were determined. In addition, the effects of factors such as antigen batch, freezing, preserving of the samples and somatic cell counts (SCCs) of the samples were evaluated. Raw optical densities (ODs) and normalized values were compared using the concordance correlation coefficient (CCC), the coefficient of variation (CV), Bland-Altman plots (BA). Based on raw OD values, there was a high repeatability within a plate (CCC approximately 0.96 and CV<10%). Repeatability between plates was evaluated following normalization of OD values by four methods. Computing normalized values as (OD-Nt)/(Pst-Nt), gave the most repeatable results, with the CCC being approximately 0.95 and the CV approximately 11%. When the OD values were higher than 1.2 and 0.3 for the positive and the negative controls, respectively, none of the normalization methods evaluated provided highly repeatable results and it was necessary to repeat the test. Two batches of the crude antigen preparation were evaluated for repeatability, and no difference was found (CCC=0.96). The use of preservative (bronopol) did not affect test results, nor did freezing the samples for up to 8 months. A significant positive relationship between ELISA OD for milk samples and SCC score was found. Therefore, the use of composite milk samples, which have less variable SCC than samples taken from each quarter, would be more suitable when the udder health status is unknown. The analytical methods used to evaluate repeatability provided a practical way to select among normalization procedures.

Dermal nematodosis in commercially captured rockfish (Sebastes spp) from coastal British Columbia, Canada.

Members of an Ahousaht First Nations community of Vancouver Island, Canada have developed a market for wild-caught species of indigenous rockfish (Sebastes spp.). The fish, which are caught by hook and line, are transported live to fish markets in Vancouver. Recently, market place downgrading of the fish has occurred due to a syndrome referred to as "black-mould", characterized by linear black disfigurations, and erosions, of the skin. Samples from 14 wild-caught rockfish were examined to determine the cause. On the basis of sub-gross and histological examination, the black-mould syndrome was attributed to intraepithelial deposition of eggs from a trichuroid nematode of the genus Huffmanela, coupled with an inflammatory response. The eggs observed in the tissues of the rockfish differed in size and morphology from those described for other species of Huffmanela. This is the first report of Huffmanela spp. infection in rockfish, probably due to a previously undescribed species.

Effects of sea lice (Lepeophtheirus salmonis Kröyer, 1837) infestation on macrophage functions in Atlantic salmon (Salmo salar L.).

Experiments were conducted to determine the effects of sea lice, Lepeophtheirus salmonis, on non-specific defence mechanisms in Atlantic salmon, Salmo salar, by experimentally infesting hatchery-reared 1 and 2 year old post-smolts, S1 and S2, with laboratory grown infective copepodids at moderate to high infection intensities ranging from 15-285 lice per fish. The effects of sea lice-induced stress were investigated by measuring the blood levels of cortisol and glucose as indicators of primary and secondary stress responses, and by changes in macrophage respiratory burst activity and phagocytosis as indicators of tertiary stress responses as well as non-specific defence mechanisms. Fish were sampled prior to sea lice infestation at day 0 and at days 3, 7, 14 and 21 post-infestation. Sea lice were at copepodid stage at day 3, at chalimus stages at days 7 and 14, and at pre-adult stage at day 21. Blood levels of cortisol and glucose were found to be significantly increased at day 21 in fish-infested with the highest levels. Macrophage respiratory burst and phagocytic activities were found to be significantly decreased only at day 21. These results indicate that sea lice do not suppress host defence mechanisms during the earlier stages of infestation. They do have effects on the development of chronic stress and on the host non-specific defence mechanisms soon after the lice reach the pre-adult stage.

Lungworm (Crenosoma vulpis) infection in dogs on Prince Edward Island.

Crenosoma vulpis is a nematode lungworm that is highly prevalent in the red fox population of Atlantic Canada. Dogs are susceptible to infection with clinical signs consisting primarily of a chronic cough. A recent report of C. vulpis infection in 3 dogs on Prince Edward Island prompted an investigation into the importance of this parasite as a cause of chronic respiratory disease in Island dogs. A general prevalence was determined through the necropsy of dogs euthanized at the local humane society. Lungs were removed and examined for parasites using a lung flush technique. Rectal feces was collected and examined for first-stage larvae using the Baermann technique and zinc sulfate centrifugal flotation. Ten of 310 dogs (3.2%) were positive with 0-35 worms (mean = 11.0 +/- 13.4) recovered. First-stage larvae of C. vulpis were recovered in the rectal feces of the one animal in which no worms were recovered on lung flush. A second survey was conducted examining fecal samples with the Baermann technique from afebrile dogs with presenting signs of chronic cough that had no history of recent anthelmintic treatment and showed no signs of cardiac disease, based on physical examination. Fifteen of 55 dogs examined (27.3%) were definitively diagnosed as C. vulpis-positive. All of the infected dogs were treated with fenbendazole (50 mg/kg body weight, p.o. q24 h for 3-7 days). Clinical signs resolved in all of the dogs and fecal samples were negative 2-4 weeks posttreatment. It was concluded that C. vulpis infection was a significant cause of upper respiratory disease in dogs on Prince Edward Island and should be considered in all dogs with presenting signs of chronic cough.

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.

Interactive mortality factors in common loons from Maritime Canada.

Between August 1992 and November 1995, 31 moribund or dead common loons (Gavia immer) found in the three Maritime provinces of Canada (New Brunswick, Nova Scotia, Prince Edward Island) were necropsied. Eight of these birds were in good body condition and died acutely from drowning or trauma. The remaining 23 birds were in poor body condition and had either chronic lead poisoning, respiratory mycosis, or oil contamination of their plumage. Loons in poor body condition had significantly higher numbers of intestinal trematodes and significantly higher levels of total renal mercury than loons in good body condition. Therefore, poor body condition in many loons was associated with two or more concurrent potential disease processes, although we could not establish a cause-effect relationship among these processes in individual birds. These results suggest that mortality in chronically ill wild animals can result from synergism among several potentially debilitating agents present in their environment.

Trichinella spiralis in sylvatic hosts from Prince Edward Island.

Larvae of Trichinella sp. were found in two of 208 red foxes (Vulpes vulpes) and one of 125 coyotes (Canis latrans) obtained from trappers from Prince Edward Island (Canada) in 1995 and 1996. A polymerase chain reaction based DNA biotyping method revealed the larvae to be isolates of Trichinella spiralis. This is the first verified identification of T. spiralis in sylvatic hosts from Canada.