Multiple pathogens found in growth-retarded black tiger shrimp Penaeus monodon cultivated in Thailand

Abstract

In 2001-2002 throughout Thailand, black tiger shrimp Penaeus monodon farmers reported very unusual retarded growth. We have called this problem monodon slow growth syndrome (MSGS). Based on decreased national production, estimated losses due to this phenomenon were in the range of 13 000 million baht (approximately US $ 300 million) in 2002. Since rearing practices had not changed, it was considered possible that the MSGS problem may have arisen from a new or existing pathogen. To examine this possibility, cultivated shrimp were sampled from 32 commercial rearing ponds that reported abnormally slow growth from eastern, central and southern regions of Thailand. Shrimp were randomly sampled from each pond and grouped into normal and small shrimp. Normal shrimp were defined as those with body weights (BW) of 24 g or more while small shrimp were defined as those that weighed 16.8 g or less. Pleopods were used for detection of monodon baculovirus (MBV), heptopancreatic parvovirus (HPV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV) using specific polymerase chain reaction (PCR) assays. In addition, some shrimp were processed for normal histopathology and transmission electron microscopy (TEM). Most of the shrimp specimens were infected by at least 1 of these viruses but many had dual or multiple infections. Prevalence of HPV and combined HPV/MBV infections in the small shrimp was significantly higher than in the normal shrimp. In addition to the viruses, a new microsporidian species, gregarines and bacteria were also observed but were not significantly associated with the MSGS problem. Some of the small shrimp gave negative results for all these pathogens by PCR and histology and no new and unique histopathology was recognized in any of the samples. The findings suggested that HPV infection was a contributing factor but not the overriding factor responsible for MSGS. It is possible that MSGS is caused by an unknown pathogen or by some other presently unknown, non-pathogenic factor. KEY WORDS: Penaeus monodon · Growth retardation · MBV · HPV · IHHNV · Microsporidian · GregarinesResale or republication not permitted without written consent of the publisher

Duplex real-time PCR for detection and quantification of monodon baculovirus (MBV) and hepatopancreatic parvovirus (HPV) in Penaeus monodon

“…In contrast, infections of larger juveniles and adults usually do not cause mortality, and the infected individuals show no symptoms of disease. However, the severity of infection, especially with regard to HPV, has been associated with growth retardation (Flegel et al 1999, Chayaburakul et al 2004). In addition, infected juvenile and adult shrimp can be carriers and constitute a serious threat to production if undetected.…”

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“…The rapid, country-wide occurrence of the problem, its tendency to be related to PL batch and the lack of association with known pathogens suggested the possible occurrence of a new infectious agent (MSGA) 2 . No conclusions can yet be made regarding this speculation, but concurrence of the problem with large-scale import and cultivation of P. vannamei opens the possibility for yet another new, cryptically introduced virus.…”

“…(Table 1) and are capable of a specific, adaptive response that cannot be explained by current knowledge and understanding of their cellular and humoral defenses. A hallmark of the arthropod response is specific tolerance to single and multiple viral infections without gross or histological signs of disease [2][3][4][5] . The concept of viral accommodation was introduced in 1998 as a simple testable hypothesis to explain this tolerance 6 .…”

Ecological Roles of Commercial Mangrove Plantation Forests for Benthic Macroinvertebrate Communities in Thailand

“…During the past decades, shrimp farming in Thailand has been experiencing outbreaks of viral diseases such as white spot syndrome and reduced shrimp production due to degradation of the environment (Flegel, 1997;Chayaburakul et al, 2004). Disease damage has been extensive, covering large areas of culture and many shrimp farms were abandoned (Dierberg and Kiattisimkul, 1996).…”