Herpes virus infection

The order of herpes viruses in known as Herpesvirales; it is a large group of viruses that includes various strains that infect humans and many types of animals through direct contact with body fluids. The herpes virus is highly contagious and is characterised by latent and recurring infections. It inhabits the cells of the body and lies dormant until it is triggered to re-emerge. Typically a life-long infection due to the viruses’ ability to evade detection by the host’s immune system.

During the active stage of the disease, herpes virus replication within cells causes development of tissue lesions in the affected area. Many strains of the herpes virus produce external blisters and sores on the skin, and these are highly contagious and can be transmittable between species. Some species of herpes virus can be transmitted between humans and animals but transmission from animals to humans is rare.

Rabbits can acquire a handful of different herpes viruses, but for pet rabbits, the most common infections are caused by Herpes simplex virus 1 (HSV-1), Herpes cuniculi (LHV-4), Herpes cuniculi (LHV-2) and Herpes sylvilagus (LHV-1/LHV-3).

HSV-1 is a form of the virus that is thought to be specific to humans, but the external lesions make it easily transmittable to other species, including pet rabbits. One of the most common ways HSV-1 can affect rabbits is by infecting the eyes. Signs of this condition can include watery eyes, squinting, conjunctivitis (redness around the eyelids), ulceration of the cornea and blindness. It is a condition that can come and go as the virus re-emerges after periods of dormancy. Exposure of the HSV-1 strain to pet rabbits has also rarely resulted in brain lesions. This condition leads to seizures, coma and death.

LHV-4 is form of the virus specific to domestic rabbits and is the most common naturally acquired strain of herpes virus in pet rabbits. It has also been seen occasionally in wild rabbits. This strain has mostly been seen in North America, and is usually found when larger colonies have been infected. It is highly contagious and young females seem more likely to be infected. The most common signs include wounds and blisters on the face, back, eyes and genitals, but other more serious signs can occur, including a swollen face, discharge from the nose and eyes, respiratory distress, anorexia and sudden death.

LHV-2 is indigenous to domestic rabbits, but causes no signs of disease, so is difficult to detect.

LHV-1 and LHV-3 are indigenous to wild cottontail rabbits and is not known to infect domestic rabbits. It causes lesions in the throat, lymph nodes, liver, kidney and spleen.

Diagnosis varies depending on the strain of the disease. For mild or common strains, the veterinarian can diagnose the disease by observing clinical signs or taking blood or tissue samples and sending them to the laboratory for analysis.

For some tests, general anesthesia may be required.

As with all viruses, treatment is aimed at supporting the animal until the virus can be largely controlled by the animal’s immune system. Since herpes viruses cannot be cured, there is no treatment that will eliminate the disease, but when the virus is active and signs of disease are seen, supportive treatment can be provided. For mild cases, this may mean giving pain relief, helping to minimise secondary bacterial infection by keeping wounds clean and administering nutrition and fluid support to help the animal recover faster. In some cases, the veterinarian may prescribe anti-viral medications to help the immune system combat the virus.

When the virus is active, the animal may be able to shed the virus to other animals, and possibly even humans, so the rabbit must be isolated from other animals and excellent hygiene adhered to at all times. Once the virus returns to a dormant phase, the animal will still be a carrier and may shed the disease to other animals so it should be housed to ensure that cross-contamination with other animals does not occur. Outbreaks of the disease can occur at any time, especially during seasonal changes or throughout periods of stress.