Showing papers by "Donald V. Lightner published in 1987"

A survey of cultured penaeid shrimp in Taiwan for viral and other important diseases

Abstract: A survey of disease problems adversely affecting cultured shrimp at farms in Southern Taiwan was conducted in March of 1986. Farms selected for inclusion in the survey were experiencing a variety disease problems in their shrimp stocks, including mortality, poor growth, and reduced food conversion efficiency. Some apparently healthy cultured penaeid stocks were also sampled and examined for signs of subclinical disease. Most of the eight facilities surveyed cultured Penaeus monodon exclusively, although two also contained other species (P. penicillatus, P. vannamei, and P. semisulcatus). These were also sampled and examined. Important virus pathogens found during the survey included the P. monodon-type baculovirus (MBV) found in both P. monodon and P. semisulcatus, and infectious hypodermal and hematopoietic necrosis (IHHN) virus disease in P. vannamei. MBV was the most prevalent major pathogen encountered in the survey, and it was found in samples of P. monodon from seven of the eight locations surveyed and in the single sample of P. semisulcatus. These findings indicate that MBV is a common infectious agent in cultured stocks of these species in Taiwan.The disease hemocytic enteritis (HE) was also commonly observed in shrimp from five of the eight locations surveyed. This may indicate that the disease, which may be caused by an enteric toxin produced by certain types of blue-green algae, is an important disease of cultured shrimp in Taiwan. Also found in the study were two idiopathic syndromes which often, but not always, occurred together in the same shrimp. The first of these syndromes was a generalized diffuse inflammatory disease (II), which was found in several populations of P. monodon and in two stocks of P. penicillatus. The other idiopathic condition, often was observed in shrimp with II, was characterized by hypertrophy of Oka's lymphoid organ, and disassociation and metastasis of spherical clumps of cells derived from the hypertrophied organ. A number of apparently ubiquitous penaeid epicommensals were observed on the gills, appendages, and general body surface of many shrimp sampled in the survey, and some were associated with disease and mortality.

IHHN disease of Penaeus stylirostris: effects of shrimp size on disease expression

Abstract: . Populations of Penaeus stylirostris, free of infectious hypodermal and haematopoietic necrosis virus (IHHNV), were divided into five size groups (PL2 [2-day-oldpostlarvae, approximately 5.0 mg], 3.7 g, 14.5 g, 21.3 g and 36.9 gaverage initial weight), and experimentally exposed to IHHNV per or. Statistical comparisons (histologically-derived) of infection severity ratings from six weekly sample periods indicated the relative abundance of pathognomonic Cowdry type A intranuclear inclusion bodies (and, hence, the severity of the disease) differed between sizes. The results of comparisons showed a tendency for larger animals to have a significantly lower prevalence of inclusion bodies and associated histopathology than smaller animals. The results also indicated that the smaller (average weight) the group was, the shorter was the period of time from initial exposure to the first histological detection of the disease. Thus, the larger (in average weight) a population of P. stylirostris is upon initial exposure to IHHNV, the less acute will be disease manifestation within a given time and the longer will be the period before the disease is first histologically detectable. A predictive equation that defines the epizootiological relationship of IHHN disease within an intensively cultured population of P. stylirostris is also presented.

Efficacy of formalin in reducing the levels of peritrichous ciliates on cultured marine shrimp

Abstract: Tests were performed to measure the efficacy of formalin in reducing peritrichous ciliates on the surface of cultured marine shrimp The tests were conducted at concentrations above and below those being used in shrimp culture and were designed to define the concentration providing the most effective rapid reduction of ciliates Penaeus stylirostris Stimpson,‘preconditioned’ in a single large tank, were divided equally (after diagnosis of significant ciliate epifaunation) into ten 1000 litre fibreglass tanks; each received 235 shrimp of 10–15 g average weight These tanks were divided into five treatments: 0, 12·5, 25, 50 and 100 ppm; two replicates per treatment Treatments were conducted under static conditions for 4 h Ciliate levels were measured on day 0 (pretreatment) and days 1, 2 and 7 post-treatment Formalin at 25, 50 and 100 ppm was demonstrated to be effective in reducing ciliates, while 12·5 ppm did not differ from the control (0 ppm) In addition, the higher the level of formalin used (within the effective range), the more pronounced was the initial ciliate reduction and the longer was the protection from further ciliate epifaunation