Myxomatosis

Myxomatosis, sometimes shortened as myxo, is a disease caused by the myxoma virus, a strain of Leporipoxvirus, that affects rabbits. It is a usually fatal disease in domestic and wild old-world rabbits and more likely when mosquitos are numerous such as the summer and fall. The virus is spread primarily through insect bites (mosquitoes, flies, fur mites, fleas, ticks), but it can also be transmitted by mechanical factors such as nonbiting insects, thorns, bedding, and food.

History
The myxoma virus was originally intentionally introduced into Australia and Europe in an effort to control wild rabbit populations; resistance has since developed. Several strains of myxoma viruses exist.

Myxomatosis can be found in Europe, South America, North America, and Australia. In the United States, the disease is seen primarily in California as an extremely virulent strain with mortality rates exceeding 99%.

Symptoms
The Myxoma virus causes a trivial infection in its natural host, either Sylvilagus brasiliensis (Tapeti, forest rabbit, found in Mexico or Argentina) or Sylvilagus bachmani (brush rabbit), which is native to California. Myxomatosis can occur in hares but infection is rare and usually mild.

For the California strain of myxo in domestic rabbits, incubation period is usually 1 to 3 days. It can attack domestic rabbits in peracute (extremely active and violent), acute, and chronic forms.

The disease starts with a skin lesion which typically develops 4 to 5 days after inoculation and enlarges to about 3 cm in diameter 9 to 10 days after infection. The eyelids become thickened and then completely closed by the 9th day with a semipurulent ocular discharge. Secondary lesions develop throughout the body, typically on the nares, lips, eyelids, and base of the ears and on the external genitalia and anus.

Rabbits vaccinated against myxomatosis can also be affected and develop an atypical form of the disease called lumpy bunny syndrome. The severity of the disease is variable and can range from a single lump to multiple skin lesions.

Treatment and prevention
Unfortunately, most treatment for myxomatsosis is non-effective, and supportive care is generally unsuccessful. Myxomatosis is usually fatal for domestic rabbits due to exhaustion from lack of nourishment or secondary bacterial infection. However, high ambient temperature of over 85&deg;F can increase recovery rate.

Rabbits with lumpy bunny syndrome have a less bleak prognosis, and many of them can recover with appropriate supportive care.

To prevent myxo, your best options are to do the following:
 * Control its vectors - add screening to keep out insects; use flea control; keep your rabbits indoors.
 * Disinfect - 10% bleach, 10% NaOH, 1% to 1.4% formalin
 * Quarantine new rabbits and do not house wild rabbits with domestic pet rabbits.
 * Vaccinate your rabbits if it is available in your country. It can provide temporary protection. Unfortunately the vaccination is not available in Australia or the United States.