Estimation of the costs of mastitis, using National Animal Health Monitoring System and milk somatic cell count data

Data collected by the National Animal Health Monitoring System in Ohio for a 12-month period during 1986 and 1987 were used to determine the relative magnitude of costs associated with mastitis in the following categories: milk production loss, veterinary services, drugs, producer labor, and "other" factors. The cost of milk loss associated with mastitis that was reported by producers cooperating in the National Animal Health Monitoring System program was compared with estimates based on bulk tank somatic cell counts and individual cow milk somatic cell counts. Using producer-reported estimates, milk loss accounted for about one third of the total cost associated with mastitis. When estimates of milk loss were replaced by estimates based on bulk tank somatic cell counts, milk loss accounted for over 80% of the total cost of mastitis. Estimates of the cost of milk loss based on studies relating milk yield to somatic cell counts differed considerably. Consequently, it was unclear how to best estimate the relative magnitude of the milk loss component of mastitis costs.     

Some effects of oral doses of oxytetracycline on growth,survival and disease in Penaeus aztecus

Two size groups of brown shrimp (Penaeus aztecus) were fed a formulated feed containing 0, 100, 1 000 or 5 000 mg of oxytetracycline/kg of feed. Growth and survival were measured after a 3-week drug consumption period. The shrimp were then inoculated with Vibrio alginolyticus, and survival was monitored during the following 24 h.At all three concentrations of oxytetracycline, small shrimp (mean initial wet weight 143.4 mg) consumed approximately one-third the amount of feed consumed by those fed the control diet with no oxytetracycline, yet growth was more rapid with diets containing 100 and 1 000 mg of oxytetracycline/kg of food than with the control diet. Larger shrimp (mean initial wet weight 458.1 mg) receiving oxytetracycline consumed about one-fourth the feed consumed by those on the oxytetracycline-free diet. Some growth inhibition was apparent in these shrimp at all oxytetracycline concentrations. Maximum drug consumption rate, based on actual feed intake, was approximately 1 300 mg oxytetracycline per kg body weight per day for small shrimp, but only 370 mg per kg body weight per day for larger shrimp.All shrimp fed 0, 100 or 1 000 mg of oxytetracycline/kg of feed died within 24 h following inoculation with a standard dose (70% light transmission at 520–540 nm) of Vibrio alginolyticus. All the small shrimp and 70% of the large shrimp fed at the 5 000-mg drug level died, but death generally took place later in the 24-h period than with those fed at the lower drug concentrations. All shrimp fed 5 000 mg oxytetracycline/kg of feed and inoculated with a 1 : 100 dilution of the standard dose of Vibrio alginolyticus survived. All small shrimp and 90% of the large shrimp survived injection of sterile saline.     

IHHN virus: Infectivity and pathogenicity studies in Penaeus stylirostris and Penaeus vannamei

Infectivity studies of infectious hypodermal and hematopoietic necrosis virus (IHHNV) were conducted on Penaeus stylirostris and P. vannamei (representing species highly susceptible and highly refractory to the disease) via intramuscular injections of the virus. Distinctive histological lesion patterns were observed between species. Six target organ systems were compared interspecifically. The gills and nerve cord/ganglia were shown to undergo significantly higher degrees of tissue damage in infected P. stylirostris compared with infected P. vannamei. Pathogenetic differences correlated well with observed differences in epizootiology between the two species.The infectivity study confirmed that IHHN disease is virus-caused. Cell-free extracts from IHHNV-infected shrimp, when injected into healthy, susceptible shrimp, produced mortalities and Cowdry type A intranuclear eosinophilic inclusion bodies presently considered pathognomonic for the disease.     

Biosecurity in Shrimp Farming: Pathogen Exclusion through Use of SPF Stock and Routine Surveillance

Biosecurity, as it is being applied to shrimp aquaculture, may be defined as the practice of exclusion of specific pathogens from cultured aquatic stocks in brood stock facilities, hatcheries, and farms, or from entire regions or countries for the purpose of disease prevention. To make a biosecurity program a functional concept in shrimp aquaculture, the relevant risks should be identified and the appropriate biosecurity measures put into practice to mitigate those risks. Examples of biosecurity measures put into place for this purpose may include such basics as site selection when the intent is to locate a new shrimp culture facility in an area where certain diseases are not enzootic. Standard facilitylfarm operating procedures can be adapted to minimize the risks of disease introduction and spread within a facility through such concepts as pretreatment of all source water, and reduced or “zero” water exchange. Stocking shrimp culture facilities with domesticated shrimp stocks that are free of specific diseases (“Specific Pathogen Free” or SPF) and or with stocks resistant to specific disease agents (SPR) is perhaps the most important single component of a biosecurity program. The example set by the development of domesticated SPF stocks of Litopenaeus vannamei has helped to make biosecure shrimp culture feasible. The development of these and other SPF stocks, and the diagnostic methods to develop and monitor them for specific diseases and disease causing agents, have been milestones in the development of the international shrimp farming industry in recent years, and it has contributed to the species rivaliig Penaeus monodon as the dominant farmed shrimp species. The regular monitoring (surveillance) of shrimp stocks in biosecure culture facilities is a necessary component of a biosecurity plan, as is having in place a contingency plan for disease containment and eradication should a breach occur in the physical and managerial components of a biosecure facility and a targeted disease occur.     

Microbial diseases of cultured lobsters: A review

Six microbial diseases of cultured American lobsters (Homarus americanus) determined to be of significant concern to commercial aquaculture are discussed in relation to present knowledge of characteristics of the causative microorganisms, lobster susceptibility, environmental influence, severity, gross and microscopic recognition, physiological changes, contagion and control. The diseases reviewed here include shell disease, Gaffkemia, microbial epibiont disease, Lagenidium disease, Haliphthoros disease, and Fusarium disease.     

Visceral leishmaniasis in the German shepherd dog. II. Pathology

Three German shepherd dogs were inoculated with Leishmania chagasi and three with Leishmania donovani and the infection was followed for 82 days. All infected dogs developed splenomegaly and lymphadenomegaly. In lymph nodes there was a reduction in lymphocyte population in paracortical areas, extensive proliferation of macrophages in paracortical areas and medullary cords, follicular hyperplasia, and increased numbers of plasma cells. The spleen had decreased numbers of lymphocytes in periarteriolar lymphoid sheaths, proliferation of macrophages in these regions, follicular hyperplasia, and enlargement of the red pulp with clusters of macrophages and plasma cells. The morphology of the tonsil was similar to the lymph nodes. Clusters of macrophages, often containing Leishmania spp, were present in liver, bone marrow, lung, and the intestines. The morphologic changes in lymph nodes and spleen were suggestive of a suppressed cell-mediated immunity and an active humoral immunity. The German shepherd dog may be a useful laboratory model for the study of immunopathologic changes in visceral leishmaniasis.     

A real‐time PCR for the detection of hepatopancreatic parvovirus (HPV) of penaeid shrimp

Hepatopancreatic parvovirus (HPV) causes a common shrimp disease that occurs in many shrimp farming regions, especially in the Indo Pacific, and infects most of the cultured penaeid species. There are seven geographic HPV isolates known, so a method to detect different HPV types is needed. We developed a sensitive and generic real‐time PCR assay for the detection of HPV. A pair of primers and TaqMan probe based on an HPV sequence obtained from samples of Fenneropenaeus chinensis from Korea were selected, and they were used to amplify a 92 bp DNA fragment. This real‐time PCR was found to be specific to HPV and did not react with other shrimp viruses. A plasmid (pHPV‐2) containing the target HPV sequence was constructed and used for determination of the sensitivity of this assay. The assay could detect a single copy of plasmid DNA, and it was used successfully in finding HPV in shrimp samples from the China‐Yellow Sea region, Taiwan, Korea, Thailand, Madagascar, New Caledonia and Tanzania.     

A dietary modification approach to improve the osmoregulatory capacity of Litopenaeus vannamei cultured in the Arizona desert

A modified diet was formulated for Arizona inland shrimp farming and tested as a method for reducing moult‐associated mortalities presumed due to trace mineral deficiencies. The experimental diet was supplemented with additional dietary magnesium, potassium, phospholipids and cholesterol to a commercial shrimp feed (Rangen 45/10, which was also used as the control diet). The modified diet was tested at Arizona Mariculture Associates (AMA), while the control diet was used at a nearby inland shrimp farm, Desert Sweet Shrimp Farm (DSSF). Both feeds were used throughout the culture season of 2001. Earthen pond‐reared Litopenaeus vannamei at intermoult stages (C‐D₀) and ranging from 7 to 30 g were sampled at intervals for determination of haemolymph osmolality (HO). Results showed that the modified diet had not only resulted in larger size shrimp at harvest, but also improved osmoregulatory capacity (OC). HO of DSSF shrimp decreased as shrimp grew bigger, whereas HO of AMA shrimp was maintained at a stable level, or showed a slightly positive linear relationship with weight. The hyper‐OC of shrimp from AMA (462 mOsm kg^?1) was greater than that from DSSF (398 mOsm kg^?1). Shrimp at AMA fed the experimental diet presented no mass moult‐associated mortalities. To further investigate the iso‐osmotic point of shrimp reared in AMA, a group of six salinity gradients were designed by mixing oceanic salts into the well water to form 5, 8.5, 11.4, 14.4, 17.8, 20.7 p.p.t. medium. HO of subadult shrimp (25 g in average) were then evaluated 48 h after they had been transferred from 5 p.p.t. pond water to the medium. Shrimp HO increased with external salinity, and a plateau formed as salinity reached at 11.4 p.p.t. and higher. The iso‐osmotic point of shrimp was estimated to be 695.5 mOsm kg^?1, equivalent to 26.1 p.p.t. in AMA well water.     

Degradation of Trifluralin in Seawater When Used to Control Larval Mycosis in Penaeid Shrimp Culture

Treflan (trifluralin, Elanco) is among the compounds used in the treatment of larval mycosis in penaeid shrimp caused by the phycomycetous fungi hagenidium sp. and Sirolpidium sp. Some culturists have reported treatments for these fungi with trifluralin to be ineffective while others have found it to be quite efficacious.
To study losses of trifluralin in seawater systems, experiments were conducted under varying conditions of aeration, lighting, and algal biomass using nominal concentrations of 19.3 to 65.5 ppb trifluralin. There was no detectable loss of trifluralin over a six hour period in seawater mechanically stirred and covered to prevent photodegradation. Under varying conditions of aeration and light, the estimated half-life of trifluralin ranged from 30 to 138 min. When diatoms were added to the seawater, trifluralin levels dropped to 4% of theoretical within two to three min. These observations confirm the need for a continuous administration for trifluralin to be effective in treating larval mycoses in penaeid shrimp hatching facilities.