As a dog owner you are fully and legally responsible for any harm or damages caused by your dog. If your dog bites a human, kills wildlife, damages property, causes a traffic accident, creates noise or other pollution, or is the direct cause of any other damage to the community, you may have to shoulder a substantial financial (if not legal) penalty. It is in your best interest then to always keep a vigilant eye on your dog in public and provide him with the obedience training and socialisation skills necessary to become a well-mannered and socially well-adjusted dog.
Safety is also a consideration. In September 2018 the US Food and Drug Administration (FDA) released a statement warning about the risk of tremors and seizures in animals treated with products containing drugs in the isoxazoline class, which are used to combat fleas and ticks. However, the FDA said it still considers the products "safe and effective".
Lungworm larvae may be present in slugs and snails, and if eaten, pets may be infected with worms that make their way to the lungs, where they block airways and make breathing difficult. Most dog wormers don't claim to treat lungworm, although some cat wormers do. Research conducted internationally has found moxidectin, which is found in some heartworm treatments for dogs, to be effective against lungworm, but this claim can't be made for dogs on packaging in Australia. Check with your vet as to whether it's an issue in your area, and discuss the best preventative treatment.
Giardia intestinalis and Giardia duodenalis are single celled protozoan parasites, which inhabit the affected dog’s small intestine, causing clinical signs of Gardiasis. The protozoa attach themselves to the intestines and multiply. They may be directly swept through the intestines and appear in the infected dog’s faeces or they may develop into a tougher more durable ‘cyst’ form, which is again passed in the dogs faeces but is able to survive for long periods in the external environment. Dogs are infected by ingesting the cysts from contaminated water and the environment. Infected dogs may not show any clinical signs of Gardiasis, but they can still shed the protozoa from their systems, spreading the infection to other healthy animals. Infection and subsequent illness is more commonly seen in younger animals. Signs of infection include: chronic or intermittent diarrhoea that may appear ‘fatty’ and slimy, accompanied by a very foul smell. Weight loss is also possible if left untreated.