Internal and External Parasites in Dogs and Cats

Internal Parasites

Internal parasites (also known as worms) are a common condition in dogs and cats needing regular veterinary monitoring and treatment. The most common internal parasites include roundworms, tapeworms, hookworms and whipworms. These worms can cause a wide range of problems from subclinical disease to clinical conditions including vomiting, diarrhea and weight loss. Some of the pet internal parasites represent a risk to human health, therefore regular monitoring is important.

We recommend routine monitoring and appropriate deworming of all dogs and cats, even when they are primarily housed indoors. Puppies and kittens are particularly susceptible to infection and deworming should be evaluated around the time of their first vaccination.

Please speak to the primary care veterinarians at CityU VMC to discuss deworming protocols for your pets.



Heartworm is a parasite that can infect dogs and uncommonly cats. The parasite is transmitted through mosquito bites and the larval worms then travelling through the blood vessels to the heart. Here, the worms grow and reproduce cause damage to the heart and lungs. Eventually, these can cause initial infections may show no clinical signs and as the parasite load increases symptoms include coughing, exercise intolerance, breathing difficulties, weakness, weight loss, abdominal distension and infection can be fatal.

Regular heartworm testing and preventative therapy are recommended.  An evaluation by a veterinarian prior to any treatment or prevention to ensure the proper plan for your pet’s heartworm testing and preventative therapy.  Significant risks including death can occur by heartworm if not evaluated by veterinarian and improper medication is used on a pet.

Please arrange an appointment with the primary care veterinarians at CityU VMC for a blood test prior to giving any heartworm prevention products.



Ectoparasites are commonly known as external or skin parasites.

Fleas and ticks are common ectoparasites of dogs and cats. Others include sarcoptes mites, demodex mites, ear mites and less commonly cheyletiella mites or lice.

General symptoms from ectoparasites may include itchiness, hair loss, weakness, reduced appetite, pale gums or changes in urine color.  “Tick fever” and flea infestations are common in Hong Kong and owners need to be mindful.

A number of preventative and treatment options are available for ectoparasites, including spot-on treatment, oral tablets, collars and sprays. Heavy infestations may require additional medicated shampoos, ear drops and environmental decontamination. Please meet with the primary care veterinarians at CityU VMC to discuss which prevention strategy or treatment is most appropriate and safe for your pets.