Herpes Virus Emerges as Prime Suspect in South Africa's Sardine Die-Off

Scientists in South Africa are investigating a herpes virus as a potential cause of the mass death of sardines along the country's west and south coasts. The event, which occurred this month, has prompted an urgent inquiry by the Department of Forestry, Fisheries and the Environment.

The virus, known as pilchard herpesvirus (PHV), has been detected in the fish. This marks the first time PHV has been identified in sardines off South Africa. The virus was previously linked to two mass sardine mortality events in Australia during the 1990s.

PHV can cause inflammation and thickening of the gills, which interferes with the fish's ability to take in oxygen. Sardines and pilchards are the same species, with sardines being the younger, smaller fish.

The department has stated that PHV poses no known risk to human health. It also clarified that the detection of the virus does not mean commercially caught or canned sardines are unsafe to eat.

Scientists from the South African Institute for Aquatic Biodiversity and a local university are examining dozens of dead and live sardines from affected areas. Initial results show that dead fish consistently had high levels of PHV, while live fish showed varied levels.

Other potential causes, such as harmful algae, unusually cold sea temperatures, or low oxygen conditions, are also being considered. However, the department says evidence increasingly points to PHV as the leading explanation.

Dalene Vosloo, a biological sciences lecturer at the University of KwaZulu-Natal, who is not part of the investigation, cautioned that the virus may not be the whole story. She noted that multiple factors could have contributed, as changes in water quality or temperature can make fish more vulnerable to disease.

The die-off has also caused operational issues. The Koeberg Nuclear Power Station, north of Cape Town, had to reduce power by 50% at one of its units after dead sardines clogged a seawater intake.