Natural infections of Angiostrongylus vasorum and Crenosoma vulpis in dogs in Germany (2007-2009)

An ELISA for sensitive and specific detection of circulating antigen of Angiostrongylus vasorum in serum samples of naturally and experimentally infected dogs

Canine angiostrongylosis is an emerging cardiopulmonary disease in Europe which can be fatal if left untreated. We developed a sandwich-ELISA based on a monoclonal antibody (mAb Av 56/1/2) and on polyclonal rabbit antibodies directed against Angiostrongylus vasorum adult excretory/secretory - antigen for the detection of circulating serum antigen of A. vasorum. The sensitivity of the test was 95.7% (78.1-99.9, 95% CI) as determined with sera of 23 dogs naturally infected with A. vasorum. The specificity was 94.0% (83.5-98.7, 95% CI) using 50 dog sera (control group) submitted for reasons other than parasitic infections. Potential cross-reactions were investigated with sera of a group of totally 61 dogs with proven infections with Dirofilaria immitis (n=23), Crenosoma vulpis (n=14), Ancylostoma caninum (n=4) or Toxocara canis (n=20). No significant difference was observed concerning the proportion of positive reactions between the control group and the group with proven helminth infections other than A. vasorum. In experimentally inoculated dogs with proven worm burdens of A. vasorum, the proportion of seropositive dogs increased over the first 3 months of infection, starting from 35 days post inoculation (dpi) which was before the onset of larval excretion. Ten weeks post inoculation, 98.6% of the dogs were seropositive, and circulating antigen persisted in two dogs with long-term follow-up over 286 and 356 days, respectively. In contrast, in dogs with a single treatment with imidacloprid/moxidectin at four or 32 dpi, no circulating antigen was observed, while in dogs treated at 88-92 dpi, OD values decreased within 13-34 days. The specific detection of circulating A. vasorum antigen by ELISA represents a valid alternative for reliable diagnosis and for follow-up investigations after anthelmintic treatment. Moreover, the test can be used for mass screening in large epidemiological investigations.

Comparison of faecal techniques including FLOTAC for copromicroscopic detection of first stage larvae of Angiostrongylus vasorum

Angiostrongylus vasorum is a metastrongylid nematode that resides in the pulmonary arteries and the right heart chambers. In dogs, infection results in respiratory, bleeding and neurological disorders and further clinical signs. In the present study, FLOTAC was evaluated for the detection of first-stage larvae (L1) of A. vasorum in canine faecal samples. This technique is based on the counting of parasitic stages (eggs, larvae, oocysts and cysts) in chambers after spinning of faecal samples onto a surface. In a first step, nine flotation solutions were evaluated using faeces of two experimentally infected dogs. Zinc sulphate (specific gravity (s.g.) 1.2) and zinc sulphate plus potassium iodomercurate (s.g. 1.45) gave good results. However, with the latter technique, the larvae were slightly deformed. Subsequently, FLOTAC, using zinc sulphate, was compared through a randomisation technique with McMaster, flotation in tube and Baermann-Wetzel technique. The mean larvae per gramme (LPG) obtained by the FLOTAC for both dogs was significantly higher (P < 0.05) than those obtained by the other three techniques (the means of the other techniques all lie below the 95% CI of the mean LPG of the FLOTAC technique). In addition, the FLOTAC results were consistent across replicates with only Poisson (or random) variation between individual replicates. The other techniques appear to be less consistent with evidence of extra-Poisson variation in at least one of the two dogs across the replicates within each technique. The FLOTAC technique may contribute to an improvement of the ability to diagnose canine lungworm infections and represent a valuable alternative for larval counting of A. vasorum in faecal samples, especially following transport or storage where there may be limited larvae viability, and larval migration techniques cannot be used.

Angiostrongylus vasorum infection in dogs: Presentation and risk factors

Infection with the nematode Angiostrongylus vasorum is an emerging cause of canine disease in Europe and part of North America, yet published data on its epidemiology in endemic areas are lacking. This study tested faecal samples from 897 dogs attending veterinary practices in the southern part of Great Britain, a long standing endemic focus. Among 790 dogs presenting with respiratory or other signs broadly suggestive of angiostrongylosis, 16% tested positive on a single Baermann's examination, compared with 2% of healthy dogs in the same catchment areas. Risk factors for positive tests included age (higher risk in younger dogs), season (more cases earlier in the calendar year), and worming history (lower risk if given milbemycin oxime in the past 12 weeks). Sex, neutering status and breed were not significant in terms of risk of testing positive. The most common clinical signs in infected dogs were respiratory, along with non-specific signs such as lethargy and exercise intolerance, while bleeding, neurological and gastrointestinal signs were also recorded. Around half the dogs sampled that showed signs of extra-pulmonary disease also had respiratory signs. Direct faecal smears and Baermann's tests read after one hour detected 56% and 83% of diagnosed cases respectively. The data confirm that A. vasorum is commonly associated with disease in endemic areas, which manifests with a broad range of signs at primary care level. Information on risk factors is useful in diagnosis and control, and forms a basis for further epidemiological investigation.

Survival of first stage larvae (L1) of Angiostrongylus vasorum under various conditions of temperature and humidity

This experiment has been conducted to evaluate the viability of Angiostrongylus vasorum L1 under different conditions of temperature and humidity. In order to assess the viability, fox faecal pellets containing first stage larvae (L1) were exposed to relative humidity (RH) 95% and 75%, and to different temperatures (5°C, 18°C) and at fluctuating conditions ranging from -5°C to +5°C. Moreover, larval viability under outdoor conditions in April was also observed. Survival of the larvae was strongly influenced by temperature; however, humidity did not show any significant influence on viability. In controlled condition, 100% of the larvae were found motile and active; whereas, around 14% and 19% of the larvae kept at 5°C remained viable at RH 95% and RH 75%, respectively after 78 h. All of the larvae kept at 18°C died after 66 h. In outdoor condition, larval survivability reduced to 18% after 66 h, and in fluctuation temperature viable larvae were observed in both control and experimental conditions (15%) after 78 h.

Canine and feline cardiopulmonary parasitic nematodes in Europe: emerging and underestimated

Cardiopulmonary nematodes of dogs and cats cause parasitic diseases of central relevance in current veterinary practice. In the recent past the distribution of canine and feline heartworms and lungworms has increased in various geographical areas, including Europe. This is true especially for the metastrongyloids Aelurostrongylus abstrusus, Angiostrongylus vasorum and Crenosoma vulpis, the filarioid Dirofilaria immitis and the trichuroid Eucoleus aerophilus (syn. Capillaria aerophila). The reasons of this emergence are little known but many drivers such as global warming, changes in vector epidemiology and movements in animal populations, may be taken into account. The purpose of this article is to review the knowledge of the most important heartworm and lungworm infections of dogs and cats in Europe. In particular recent advances in epidemiology, clinical and control are described and discussed.