The World Health Organization (WHO) reported on 8/3/05 that the Ministry of Health in China has reported 206 cases of human disease associated with an outbreak of Streptococcus suis in pigs. 38 of these human cases have been fatal and, as reported by China, 18 more patients are critically ill. Almost all of these cases have been from the Sichuan Province which has pone of the largest pig populations in China.

Investigation and containment of the outbreak have been given high priority by Chinese authorities. Investigations conducted by Chinese epidemiologists indicate that the first human cases occurred at the end of June. From late June through July 21, 1005, the authorities reported 20 cases of illness, of unknown cause, admitted to three hospitals in that city. WHO was officially informed of the outbreak on July 22, 2005, at which time 20 cases and 9 deaths had been reported.

Most cases reported have occurred in adult male farmers. Information reported to WHO suggests that close contact with diseased or dead pigs is the principal source of human infection. Local experts are conducing active searches for further cases. To date, Chinese authorities say they have found no evidence of human-to-human transmission.

What is Streptococcus suis? 

Streptococcus suis is a species of bacterium found in many parts of the world where pigs are raised; it is most adapted to domesticated pigs but can be found in wild boars and other animals. Infection in pigs is usually asymptomatic, but can result in blood poisoning (septicemia), meningitis, pneumonia and arthritis. Young pigs are more at risk but all ages can get the disease, compounding factors include raising pigs in poor housing with inadequate ventilation under conditions that cause stress and subsequent immune suppression.

How do humans get Streptococcus suis?

Transmission to humans is most likely to occur through wounds on the skin, including minor abrasions. But infection via ingestion or through mucous membranes—such as the conjunctiva—has been suspected in some cases. The incubation period ranges from a few hours up to three days.

What are the symptoms of the disease?

The incubation period is for Streptococcus suis is short and the disease progression is rapid. Initial symptoms include a high fever, malaise, nausea, and vomiting. Permanent hearing loss due to auditory nerve involvement occurs in about 50 % of the cases. Severe cases may be followed by meningitis, subcutaneous hemorrhage, toxic shock syndrome, and coma and may lead to severe damage of many vital organs. It is diagnosed by finding the bacteria in either blood, cerebrospinal or joint fluid.

What is the treatment for Streptococcus suis?

Early diagnosis and prompt treatment with antibiotics can lead to recovery. Delay in treatment will adversely affect the outcome and if toxic shock syndrome develops, it is only partially responsive to antibiotics and the outcome is likely to be worse.

Who is at risk?

The most important risk factor in acquiring the infection is contact with pigs or uncooked pig products, typically farmers, veterinary personnel, slaughterhouse workers and butchers. Individuals who are immunosuppressed, including those who have had their spleens removed, are also at increased risk. 

Can this disease be prevented?

Prevention of the disease in humans depends upon control in pig populations. This presents a difficult challenge to veterinary authorities and the pig industry. In serious outbreak situations, there should be strict controls on animal movements and slaughtering. The second line of defense relies on increasing awareness of the disease within those at highest risk. Awareness should extend to everyone who prepares and cooks pork, including those doing so in their homes.

Travelers Precautions 

Those traveling to China are advised to:

• Avoid places such as pig farms and markets where live pigs are raised or kept, and avoid contact with sick or dead pigs.
• As with other infectious illnesses, one of the most important preventive practices is careful and frequent hand washing. Cleaning your hands often, using either soap and water or waterless alcohol-based hand rubs, removes potentially infectious materials from your skin and helps prevent disease transmission.
• If you have open wounds on your hands, wear gloves when handling raw or uncooked pork. Wash hands before and after handling raw foods, clean utensils thoroughly after preparation of food.
• Adequate cooking is essential; the WHO recommends that pork should be cooked to reach an internal temperature of 70°C (158°F), or until the juices are clear rather than pink.
• Travelers in Southern China are recommended to avoid consuming pork meat until further notice and there is full control of this epidemic outbreak.

Source: Centers for Disease Control (CDC) and World Health Organization (WHO)