It is important to recognise that parasite elimination does not occur immediately following treatment; therefore, it is considered sensible to wait a minimum of 2 weeks after treatment before retesting and rescheduling surgery. In addition, to confirm normalisation prior to proceeding with surgery, it is recommended to carry out the reassessment of haematology( with or without biochemistry), coagulation parameters, and buccal mucosal bleeding time( BMBT) or thromboelastography, where available. When a dog tests positive, other dogs within the same household should also be tested, as they may have shared exposure risks.
An alternative approach is to ensure that all canine surgical candidates have received, with full owner compliance, a licensed treatment product against A. vasorum. As with treatment protocols, parasite death is not instantaneous so it is advisable to allow a period of at least 2 weeks following administration before undertaking elective surgery.
Treatment
Rapid use of a licensed antiparasitic treatment is indicated following confirmation of a diagnosis. In the UK, this should be a product licensed according to the prescribing cascade; Table 2 shows the current options available, with the final choice often down to the individual clinician ' s preference. Fenbendazole is also widely used, despite the lack of a licensed indication for the treatment of A. vasorum [ 13 ]. Consideration of the route of delivery( oral versus spot-on formulations) may also be relevant for some pet owners and veterinary surgeons.
Additional supportive treatment should be provided as necessary. For example, supplemental oxygen, bronchodilators, corticosteroids and mucolytics may be useful for dogs showing respiratory signs. Blood products( such as whole blood transfusion, packed red blood cells, fresh frozen plasma) may be useful for patients showing signs of haemorrhage or other documented coagulopathy. If secondary immune-mediated thrombocytopenia( described rarely) is suspected, then immunosuppressive doses of corticosteroids should also be considered.
Tranexamic acid( TXA) is an antifibrinolytic agent used in veterinary and human medicine. In brief, this drug helps prevent fibrinolysis by stopping plasminogen from binding fibrin, thereby increasing‘ clot stability’. The use of TXA has been described in dogs that are hyperfibrinolytic due to A. vasorum, showing therapeutic benefits in some cases [ 8 ]. However, dogs infected with A. vasorum may be hypercoagulable, and, therefore, empirical use of TXA should be carefully considered, balancing the risks of bleeding and thrombosis in each individual case.
Prevention
With the potential for such serious consequences after infection, prevention of A. vasorum disease is a very important consideration. Advice to dog owners should include the following:
• Keep dogs up to date with a full worming regimen
• Undertake daily disposal of faeces from gardens or other dog-walking areas
• Undertake careful cleaning of toys and bowls that are used outside( Figure 3)
• Try to‘ fox proof’ gardens, where possible
• Learn about the risks of A. vasorum
• Ensure suspected cases of A. vasorum are diagnosed and managed promptly
• Bear in mind that steps to rid the environment of slugs and snails are not effective and, moreover, can be dangerous, given that slug and snail bait carries a risk of toxicity to dogs.
Avoidance of risk factors( such as exposure to slugs / snails) is possible to some degree, but residual risk remains in dogs with outdoor access in endemic areas.
Table 2. Products licensed in the UK for the treatment of Angiostrongylus vasorum in dogs.
Drug Dose Administration route and frequency Sarolaner / moxidectin / pyrantel
1.2 – 2.4 mg / kg sarolaner 0.024 – 0.048 mg / kg moxidectin 5 – 10 mg / kg pyrantel
Single oral dose( repeated after 30 days as required)
Imidacloprid / moxidectin
10 – 25 mg / kg imidacloprid 2.5 – 6.25 mg / kg moxidectin
Single spot-on dose( repeated after 30 days as required)
Milbemycin oxime( single agent) 0.5 mg / kg Oral, once weekly for 4 weeks
24 Veterinary Nursing Journal