A case of natural co-infection of Tilapia Lake Virus and Aeromonas veronii in a Malaysian red hybrid tilapia ( Oreochromis niloticus × O . mossambicus ) farm experiencing high mortality

Abstract

This paper reports a case of natural co-infection of Tilapia Lake Virus (TiLV) and Aeromonas veronii in a Malaysian red hybrid tilapia (Oreochromis niloticus × O. mossambicus) farm. In May 2017, a tilapia farm operator reported a mass mortality among cultured red hybrid tilapia juveniles, approximately 45 days after introduction into earthen ponds. Affected fish showed lethargy, loss of appetite, swim near the pond edge, pale and isolated from schooling group. There were skin redness and haemorrhages, particularly at the operculum area and at the base of dorsal, caudal and anal fins. Histopathological examinations revealed swollen hepatocytes, haemorrhagic spleens and perivascular cuffing consisted of mononuclear cells in the brains. PCR and sequence analyses confirmed the presence of TiLV and A. veronii in the diseased fish. Phylogenetic tree revealed that Malaysian's TiLV strain was more closely related with the virus isolated in Israel than in Egypt or Thailand, while Malaysian's A. veronii strain 5L was closely related with strains from China. TiLV infection is a significant threat to global tilapia industry. However, synergistic co-infection of TiLV and other bacterial might aggravate the problem.

In vitro propagation of tilapia lake virus in cell lines developed from Oreochromis mossambicus

“…Previous studies revealed that the TiLV was found to be a serious viral pathogen and very contagious in Nile and red tilapia, making it a serious threat to tilapia culture worldwide. Previous studies also revealed that Nile and red tilapia are highly susceptible to TiLV (Amal et al, ; Behera et al, ; Eyngor et al, ; Tattiyapong et al, ). Hence, it is important to investigate TiLV infection in other fish species and to identify the natural potential carriers or reservoirs for this killer virus.…”

First detection of tilapia lake virus (TiLV) in wild river carp (Barbonymus schwanenfeldii) at Timah Tasoh Lake, Malaysia

“…At present, TiLV has been reported in several Asian countries. Several publications and notifications to the OIE have been made by the Chinese Taipei (OIE, ), India (Behera et al., ), Israel (OIE, ), Thailand (OIE, ), Malaysia (Amal et al., ; OIE, ) and the Philippines (OIE, ). Other than the above countries, Ecuador, Colombia and Egypt have also been reported to be affected by TiLV (Fathi et al., ; Ferguson et al., ; Tsofack et al., ).…”

“…Mortality of other fish species such as river barb, catfish and peacock at the beginning of the incidence may indicate a water quality problem at the base of the lake as these species of fish usually stay at the bottom of the lake. Low oxygen content at deeper area and at water inlet together with secondary bacterial infection may cause stress to these fish and unfortunately enhance the TiLV infection to river barb (Amal et al., ).…”

Virucidal effects of common disinfectants against tilapia lake virus

“…Tilapia is currently the second most frequently farmed fish worldwide, in part because of its fast growth rate and tolerance to changes in environmental conditions, as well as the fact that it is an inexpensive source of protein and maintains stable market prices (FAO, ; Rakocy, ). However, recent outbreaks of a new tilapinevirus named tilapia lake virus (TiLV), which is associated with high mortality rates, have had a significant impact on tilapia aquaculture in many countries (Amal et al, ; Bacharach et al, ; Eyngor et al, ; Kembou Tsofack et al, ; Nicholson et al, ; Surachetpong et al, ). TiLV, which is the same virus that caused syncytial hepatitis of tilapia (SHT), was first reported in Lake Galilee in Israel (Eyngor et al, ) and during an investigation of the aetiology of mass juvenile tilapia mortality in Ecuador (Ferguson et al, ).…”