Health & Medical hepatitis

Hepatitis E: Clinical Manifestations and New Developments

Hepatitis E: Clinical Manifestations and New Developments

Sources and Route of Infection

Genotypes 1 and 2

Genotypes 1 and 2 are found in developing countries in areas of poor sanitation (Fig. 1). Transmission is by the faeco-oral route via contaminated water supplies. In outbreaks, person-to-person spread is thought to be uncommon. However, recent studies from Uganda showed that household factors may be more important than previously thought.

(Enlarge Image)

Figure 1.

Worldwide distribution of hepatitis E virus (HEV) by genotype. Areas left blank are those with no or little data.

Genotypes 3 and 4

In most cases of autochthonous (locally acquired) hepatitis E in developed countries, the source and route of infection cannot be identified. However, the evidence suggests that most cases may be due to consumption of uncooked or undercooked infected pork or game (wild boar and deer) meat. HEV genotypes 3 and 4 are found in pigs throughout the world. The pig is considered the primary host for HEV, and when infected has no symptoms.

Hepatitis E virus has been documented in the food chain in a number of countries. HEV RNA was found in 11% of pig livers obtained from grocery stores in the United States and was found to be fully infectious. In the UK, the presence of HEV has also been documented in retail pig liver and recently was also found in 10% of pork sausages. Studies from southern France demonstrated HEV in figatelli pig liver sausage, a local delicacy that is often consumed without cooking. Consumption of figatelli has been linked to outbreaks of hepatitis E in this setting.

In Japan, the consumption of wild boar and deer has also demonstrated zoonotic transmission of HEV genotypes 3 and 4. Of ten patients who contracted sporadic acute or fulminant hepatitis E between 2001 and 2002 in Hokkaido, Japan, nine had a history of consuming grilled or undercooked pig liver or intestine 2–8 weeks before the disease onset. Raw pig liver sold in grocery stores in Hokkaido was also tested for the presence of HEV. Two isolates from the livers had 100% identity with two of the patients suggesting that this may have been the source of infection. The thermal stability of HEV has been investigated. HEV remains viable even after heating to 56 °C for 60 min with 1% of infectious viral particles remaining. Cooking to temperatures of 71 °C for 20 min is required to fully inactivate the virus.

Evidence has also shown that direct contact with pigs is another possible route of transmission of HEV. Seroprevalence studies in the United States show that pig handlers and veterinarians are more likely to be anti-HEV IgG positive (indicating previous exposure), compared with the normal population.

The waterborne route of infection may also be important for HEV genotypes 3 and 4. HEV genotype 3 has been detected in untreated wastewater, swine manure, swine slurry storage facilities and river water. In one of these studies, HEV found in environmental samples was shown to be viable and infectious. How long HEV can remain viable outside its primary host is not known. Factors that affect the viability of HEV in the environment are also unknown. The risk of using infected pig manure on farmland also remains to be determined. There is currently no evidence to suggest that person-to-person spread occurs with HEV genotypes 3 or 4.

You might also like on "Health & Medical"

Leave a reply