Diseases Animals Contract From Overcrowding in Pet Shelters

Updated November 21, 2016

A well-run pet shelter isolates newly acquired animals from the general population until it can assess their condition. Overcrowded pet shelters, without space to segregate newcomers, often add newly acquired animals to any space available. Overcrowding in the shelters increases stress and lowers the immune systems of the general population. Even though the general population is healthy, introducing animals without examination encourages the spread of disease.


Both canine and feline distemper, very contagious viral infections, affect the nervous system and respiratory systems. Early symptoms resemble a cold, with eye and nose discharge, which spread the virus, followed by vomiting and diarrhoea. Although puppies and kittens seldom survive, adult animals often do with intensive care. Routine immunisation provide protection against distemper.

Canine Parvovirus (Parvo)

The parvovirus causes severe vomiting and diarrhoea, often fatal for young puppies. Older dogs may survive it. Once introduced into a kennel or shelter, this is difficult to eliminate. The parvovirus can survive many disinfectants although undiluted bleach will kill it. Routine immunisation combinations usually protect against parvo.

Canine Coronavirus

Usually coronavirus only occurs in puppies. The symptoms may be mistaken for parvo. According to The University of Florida College of Veterinary Medicine, infection risk increases when dogs live together in close quarters. It is very contagious and spread by sneezing and coughing. Routine puppy shots usually protect against coronavirus.

Canine Bordetella (Kennel Cough)

Kennel cough often occurs along with parvo or distemper, as it is highly contagious and already-sick dogs are very susceptible. Kennel cough does not usually pose a problem for an adult dog in a home situation. However, in overcrowded shelters, it is difficult to control.

Feline Infectious Peritonitis

Feline infectious peritonitis spreads easily where there is more than one cat. Auburn University College of Veterinary Medicine notes this virus may cause respiratory infections or intestinal troubles. Although often fatal, some cats survive this virus with care.

Feline Leukemia

Feline leukaemia often causes cancers in cats. Even if they avoid the tumours, infected cats have lowered immune systems, making them susceptible to other illnesses. Although it spreads easily, there is a vaccine. Cornell University College of Veterinary Medicine states that cats living with other cats are most at risk, as infected cats are sources of the spread of the infection through saliva and nasal secretions.


Ringworm, a fungus infection that can affect any animal, causes hair loss and scaly skin. The areas often itch. The infection can spread easily and often spreads throughout the population of a shelter. Ringworm can also spread to humans.


Fleas and ear mites often spread quickly through overcrowded shelters. Fleas are not difficult to treat. However, once introduced, they spread quickly. Ear mites can be difficult to eliminate and affects all animals, but mostly cats. Treatment for ear mites takes some time as you must clean and treat the ears daily.

Intestinal Parasites

Tapeworms, roundworms and hookworms, common parasites, spread through faeces and fleas. Symptoms include diarrhoea, vomiting and weight loss. Animals with roundworms may exhibit a protruding stomach.

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