Horizontal transmission of white spot syndrome virus (WSSV) between red claw crayfish (Cherax quadricarinatus) and the giant tiger shrimp (Penaeus monodon)

Australian red claw crayfish, Cherax quadricarinatus was introduced into Thailand in the 1990s and is generally cultured in rice fields in many parts of the country including those where penaeid shrimp are farmed. As yet, there have been no reports of disease outbreaks in red claw caused by white spot syndrome virus (WSSV), the most serious penaeid-shrimp viral pathogen. Due to the close proximity of farms for red claw and penaeid shrimp, it is useful to know whether there is any risk of WSSV cross-infection between the two. Here we show that red claw is susceptible to WSSV infection by injection or by feeding with WSSV-infected giant tiger shrimp and that this can lead to high mortality. By contrast, co-habitation with WSSV-infected giant tiger shrimp did not lead to infection or subsequent mortality in the crayfish for up to 30 days post exposure. In contrast, WSSV could be transmitted to giant tiger shrimp within 4 days after co-habitation with WSSV-infected red claw. WSSV infections were confirmed by PCR detection, histopathology and immunohistochemistry. These results revealed that red claw is susceptible to infection and disease caused by WSSV and can transmit WSSV to the giant tiger shrimp by feeding and co-habitation. Thus, penaeid shrimp and crayfish farmers in Thailand should be aware of this possible horizontal transfer of WSSV, especially in low salinity areas where both species are cultivated or where exotic red claw have now become established.