Rabies is a deadly but preventable virus that can affect all mammals, including humans. The canine-maintained variant of rabies, eradicated in the US in 2007, remains active in over 100 countries and is responsible for most human rabies deaths globally.

Several rabid dogs have been imported into the US, including a stray puppy from Thailand brought in through LAX in 2004. Infected dogs can incubate the virus for 2 weeks to 3 months before symptoms appear and may initially seem healthy.

Canine flu is a highly contagious respiratory disease in dogs. While it currently poses little risk to people, it can cause mild to severe illness in dogs and may be fatal. The virus is not endemic to the United States but has been introduced repeatedly through dogs imported from Asia. Occasionally, new strains of flu in dogs in Asia are reported, and they could be imported via a sick dog. Other flu strains circulating internationally continue to pose a threat through imported animals.

LA County experienced its largest outbreak of canine flu from July 2021 to January 2022, linked to a dog imported from China. This outbreak resulted over 1300 illnesses in dogs, and 21 dog deaths.

Leishmaniasis is caused by a parasite transmitted via sandflies. It can take many forms and can be fatal if not treated. Infected dogs remain lifelong reservoirs.

It is endemic in tropical and subtropical regions of Asia, Africa, Southern Europe, the Middle East, and the Americas. It is rare in the US and often hard to diagnose. Cases in the US are increasing, partly due to pet importation.

Between 2011 and 2024, four dogs with leishmaniasis were imported into LA County—two from Armenia and two from Turkey. Additional suspected cases were not tested.

The parasite can incubate for over a year, so infected dogs may initially appear healthy.

Brucellosis in dogs is caused by Brucella canis, a bacterium that affects reproductive organs in dogs and can lead to infertility, spinal infections, and more. Although antibiotics can be used to treat dogs, dogs usually do not clear the infection. Humans can become infected after handling infected dogs or bodily fluids such as urine.

Symptoms may be subtle and develop over time. Infected dogs may incubate the bacteria for months without showing signs. Dogs with Brucella canis typically remain infected for life.

Since 2009, there have been growing outbreaks of Rocky Mountain Spotted Fever (RMSF) spread by Brown Dog Ticks in northern Mexico. In recent years, an increasing number of human cases of RMSF have been reported from the municipal areas of Mexicali and Tijuana, where many rescued dogs originate. Studies show that dogs in those areas have a higher rate of exposure to Ehrlichia and Anaplasma (other types of bacteria that can be found in infected ticks and passed on through tick bites).

Brown Dog Ticks infest yards and homes and can be difficult to eradicate once an infestation becomes large.

Dogs adopted from these areas should always be carefully checked for ticks and treated for ticks before they are transported. If appropriate, they should be tested and treated if needed for these diseases before transport.

References:

• Foley J. et al. (2024) – RMSF emergence in the US and Mexico
• Backus L. et al. (2022) – Tick-borne pathogens in sheltered dogs

TVT is a contagious cancer of dogs. It does not spread to people, cats, or other animals. Cancer cells can spread from dog to dog through mating, or through bite wounds. Tumors can be invasive and extensive in some cases. Fortunately, TVT usually responds well to chemotherapy and is often curable.

TVT is found in stray dogs in many countries in the world. However, it is currently rare in LA County and few veterinarians have direct experience with it here. Between 2021 and May 2025, eight cases of TVT in dogs imported from Mexico were reported in LA County. An additional case was reported in a stray dog in LA County in 2025.

References:

• Merck Veterinary Manual – Transmissible Venereal Tumor

Imported pets may arrive without proper vaccinations or parasite prevention. Many have been diagnosed with preventable diseases such as parvovirus, distemper, or intestinal worms.

Multiple dogs imported to the LA County area from Asia and from other parts of the US have tested positive for heartworm. This shows that many imported pets may not be receiving important preventative care prior to being shipped to LA County.