Epidemiological Study of the Factors that Influence Mortality and Economics on a Commercial Catfish Farm

A Catfish Management Database (CMD) was developed to analyze data from large commercial catfish farms. The CMD was developed so that data collected by the farm could be used for management of the farm and for identifying some of the risk factors associated with important bacteria diseases. This database was designed to 1) to incorporate production data already being recorded for generating reports for use at weekly managerial meetings focused on feeding rates, feed conversion ratios, mortalities and harvesting events 2) be easily used by a catfish farmer to collect management data in order to analyze production efficiency through a series of farmer defined management reports and 3) provide the farm with easy access to management reports. Additional customized reports can be generated as requested by the farm management. The next objective of this research was to determine pond level risk factors associated with columnaris disease and Enteric Septicemia of Catfish related mortalities. The data from the CMD was used to produce two publications detailing the analysis of the data and production of a univariate and multivariate models of pond level risk factors associated with both diseases. These studies showed some commonly recorded production variables were associated with either columnaris and/or ESC associated mortalities and if monitored could help identify “at risk” ponds prior to disease outbreaks. A study was then conducted to examine the cost associated with mortality on Mississippi commercial catfish farms. The mortalities examined included ponds that had mortalities from columnaris disease, ESC and then any ponds that had mortalities from either. The cost of each disease was determined along with other factors such as pond age, feed conversion ratio and feed cost that influence the profitability of a commercial catfish farm

Seasonal climatic niche and migration movements of Double-crested Cormorants

Avian migrants are challenged by seasonal adverse climatic conditions and energetic costs of long-distance flying. Migratory birds may track or switch seasonal climatic niche between the breeding and non-breeding grounds. Satellite tracking enables avian ecologists to investigate seasonal climatic niche and circannual movement patterns of migratory birds. The Double-crested Cormorant (Nannopterum auritum, hereafter cormorant) wintering in the Gulf of Mexico (GOM) migrates to the Northern Great Plains and Great Lakes and is of economic importance because of its impacts on aquaculture. We tested the climatic niche switching hypothesis that cormorants would switch climatic niche between summer and winter because of substantial differences in climate between the non-breeding grounds in the subtropical region and breeding grounds in the northern temperate region. The ordination analysis of climatic niche overlap indicated that cormorants had separate seasonal climatic niche consisting of seasonal mean monthly minimum and maximum temperature, seasonal mean monthly precipitation, and seasonal mean wind speed. Despite non-overlapping summer and winter climatic niches, cormorants appeared to be subjected to similar wind speed between winter and summer habitats and were consistent with similar hourly flying speed between winter and summer. Therefore, substantial differences in temperature and precipitation may lead to the climatic niche switching of fish-eating cormorants, a dietary specialist, between the breeding and non-breeding grounds

Large- and Small-Scale Climate Influences Spring Migration Departure Probability of American White Pelicans

Endogenous (e.g., age and sex) and exogenous (e.g., climate and resource availability) factors influence avian migration phenology. However, little is known regarding the migration ecology of birds at the non-breeding grounds, including the American white pelican (Pelecanus erythrorhynchos). We used Global Positioning System transmitters to track the movements and migration of 51 pelicans from 2002 to 2012. We used the Kaplan–Meier model to estimate pelican spring migration probabilities to quantify partial migration with 94 spring migration events and used the Cox proportional hazards model to evaluate the effects of the North Atlantic Oscillation index (NAOI), Southern Oscillation Index (SOI), and spring daily precipitation on the propensity of pelican spring migration departures. Increases in the NAOI and SOI enhanced the propensity of pelican spring departure. The propensity of spring departure was also positively related to daily precipitation. Male pelicans have greater spring migration probabilities than female pelicans. Spring migration departure probabilities of adult pelicans are greater than those of immature pelicans. Therefore, both large-scale and local climatic conditions affect pelican spring departure probabilities. Advanced migratory phenology of pelicans caused by climate changes with warming temperature and increased precipitation may result in the mismatch of pelican spring arrival with food resource availability of breeding grounds and subsequent pelican population declines

Seasonal variation and tracking of climate niche of a migratory bird

Migratory birds inhabit different areas during breeding and non-breeding seasons. Depending on the time of the year, they may utilize different resources available in seasonal habitats, but also are subjected to changing climate regimes during their annual life cycle. Migratory birds may adopt ecological niche tracking to cope with different environmental conditions between breeding and non-breeding grounds. The American White Pelican (Pelecanus erythrorhynchos, hereafter ‘AWPE’) is a short-distance migrant between the Gulf of Mexico coastal regions (nonbreeding grounds) and the Northern Great Plains (breeding grounds) of Canada and the US. The American White Pelican is a piscivore, feeding on fish, crayfish, and salamanders in inland freshwater wetlands. Cold, icy winter weather conditions substantially reduce and limit food resource availability at the breeding grounds during winters. Thus, we hypothesize that AWPEs would migrate between the breeding and non-breeding grounds to track climatic conditions that allow easier availability of resources. However, the niche tracking strategies have not been tested in AWPEs mainly due to the lack of reliable tracking data. Our objectives were to test whether the niche tracking or niche switching hypothesis would better explain seasonal variations in ecological niche overlap of AWPEs using the GPS locations of 19 tracked migrating birds, which had GPS locations at both breeding and non-breeding grounds. We estimated overlap of climate niche to test for seasonal niche tracking behaviors at both individual and population levels. Our results indicate that six out of 13 GPS-tracked AWPE individuals tracked climatic niche during the annual migration cycle. The analysis of the combined data of all 19 tracked AWPEs demonstrated that AWPEs tracked seasonal climate niche at the population level. Cold winter temperatures below zero (℃) may freeze the water surface of wetlands and shallow waterbodies, preventing AWPEs from acquiring sufficient food. The coupling of winter food resources with winter climatic conditions may result in climate niche tracking. Variation in climate niche tracking among individuals may offer ecological plasticity for AWPEs to cope with climatic changes

THE EFFECT OF ARTIFICIALLY EXTENDED PHOTOPERIOD DURING LACTATION ON MATERNAL PERFORMANCE OF THE SOW

A 20-stall farrowing facility was partitioned into two separate rooms of 10 stalls each so that photoperiod could be controlled. In addition, temperature and air movement were equalized in the two rooms. The two light regimens utilized were 8 h light: 16 h dark, and 16 h light:8 h dark. A total of 26 sows in two replicates were used. Females were moved into the facility on d 103 -+2 of pregnancy, litters were equalized at birth and weaning was at 28 d of age. Traits evaluated included litter size at birth and weaning, 21-d pig and litter weights, milk yield on d 15, survival rate and number of days from weaning to estrus for the sow. The number of pigs born alive was similar across treatments. However, after equalization of litter size, differences in the number weaned/ litter were significant (P\u3c.05) as sows exposed to 16 h of light weaned approximately one pig more per litter. The survival rate within each litter from birth (after equalization) to 21 d of age was greater (P\u3c.05) for sows exposed to 16 h light (91.2%) than for those from sows exposed to 8 h light (81.5%). Milk yield at d 15 was measured for 21 of the sows. The sows exposed to 16 h light produced significantly more milk (P\u3c.05) than sows exposed to 8 h light. The time from weaning to first estrus was similar for each treatment group

THE EFFECT OF ARTIFICIALLY EXTENDED PHOTOPERIOD DURING LACTATION ON MATERNAL PERFORMANCE OF THE SOW

A 20-stall farrowing facility was partitioned into two separate rooms of 10 stalls each so that photoperiod could be controlled. In addition, temperature and air movement were equalized in the two rooms. The two light regimens utilized were 8 h light: 16 h dark, and 16 h light:8 h dark. A total of 26 sows in two replicates were used. Females were moved into the facility on d 103 -+2 of pregnancy, litters were equalized at birth and weaning was at 28 d of age. Traits evaluated included litter size at birth and weaning, 21-d pig and litter weights, milk yield on d 15, survival rate and number of days from weaning to estrus for the sow. The number of pigs born alive was similar across treatments. However, after equalization of litter size, differences in the number weaned/ litter were significant (P\u3c.05) as sows exposed to 16 h of light weaned approximately one pig more per litter. The survival rate within each litter from birth (after equalization) to 21 d of age was greater (P\u3c.05) for sows exposed to 16 h light (91.2%) than for those from sows exposed to 8 h light (81.5%). Milk yield at d 15 was measured for 21 of the sows. The sows exposed to 16 h light produced significantly more milk (P\u3c.05) than sows exposed to 8 h light. The time from weaning to first estrus was similar for each treatment group

Fish Eating Birds Can Spread Bacterial Diseases Between Catfish Ponds

Severe outbreaks of Motile Aeromonad Septicemia disease in commercial catfish aquaculture ponds have been associated with a virulent Aeromonas hydrophila strain (VAh) that is genetically distinct from less virulent strains. We demonstrated that Great Egrets (Arde alba), Double-crested Cormorants (Phalacrocorax auritus), American White Pelicans (Pelecanus erythrorhynchos), and Wood Storks (Mycteria americana) can carry and shed viable VAh after consuming fish infected with Vah. Edwardsiella ictaluri and E. tarda are considered the primary species of Edwardsiella to cause disease outbreaks in North American catfish aquaculture. Genetic analysis has determined that most isolates designated as E. tarda were actually a new species, E. piscicida. There has been an increase in E. piscicida diagnostic cases in recent years possibly due to an increase in hybrid (Channel x blue) catfish production. We conducted a study to determine if Great Egrets (Ardea alba) shed viable E. piscicida when fed catfish infected with the bacteria. Great Egrets fed infected fish shed viable E. piscicida bacteria for multiple days, (Table 1), after last consuming infected fish on day 2 of the study. Great Egrets in the control group did not shed the bacteria. Given that Great Egrets can shed viable E. piscicida after consuming diseased fish, we hypothesize that they could also serve as a reservoir for E. piscicida and could spread the pathogen while predating fish in catfish ponds. Additional research is needed to determine if this shedding could cause disease in these ponds

Potential of Double-crested Cormorants (\u3ci\u3ePhalacrocorax auritus\u3c/i\u3e), American White Pelicans (\u3ci\u3ePelecanus erythrorhynchos\u3c/i\u3e), and Wood Storks (\u3ci\u3eMycteria americana\u3c/i\u3e) to Transmit a Hypervirulent Strain of \u3ci\u3eAeromonas hydrophila\u3c/i\u3e between Channel Catfish Culture Ponds

Aeromonas hydrophila is a Gramnegative bacterium ubiquitous to freshwater and brackish aquatic environments that can cause disease in fish, humans, reptiles, and birds. Recent severe outbreaks of disease in commercial channel catfish (Ictalurus punctatus) aquaculture ponds have been associated with a hypervirulent Aeromonas hydrophila strain (VAH) that is genetically distinct from less virulent strains. The epidemiology of this disease has not been determined. Given that research has shown that Great Egrets (Ardea alba) can shed viable hypervirulent A. hydrophila after consuming diseased fish, we hypothesized that Doublecrested Cormorants (Phalacrocorax auritus), American White Pelicans (Pelecanus erythrorhynchos), and Wood Storks (Mycteria americana) could also serve as a reservoir for VAH and spread the pathogen during predation of fish in uninfected catfish ponds. All three species, when fed VAH-infected catfish, shed viable VAH in their feces, demonstrating their potential to spread VAH

Individual-Level Antibody Dynamics Reveal Potential Drivers of Influenza A Seasonality in Wild Pig Populations

Swine are important in the ecology of influenza A virus (IAV) globally. Understanding the ecological role of wild pigs in IAV ecology has been limited because surveillance in wild pigs is often for antibodies (serosurveillance) rather than IAVs, as in humans and domestic swine. As IAV antibodies can persist long after an infection, serosurveillance data are not necessarily indicative of current infection risk. However, antibody responses to IAV infections cause a predictable antibody response, thus time of infection can be inferred from antibody levels in serological samples, enabling identification of risk factors of infection at estimated times of infection. Recent work demonstrates that these quantitative antibody methods (QAMs) can accurately recover infection dates, even when individual-level variation in antibody curves is moderately high. Also, the methodology can be implemented in a survival analysis (SA) framework to reduce bias from opportunistic sampling. Here we integrated QAMs and SA and applied this novel QAM–SA framework to understand the dynamics of IAV infection risk in wild pigs seasonally and spatially, and identify risk factors. We used national-scale IAV serosurveillance data from 15 US states. We found that infection risk was highest during January– March (54% of 61 estimated peaks), with 24% of estimated peaks occurring from May to July, and some low-level of infection risk occurring year-round. Time-varying IAV infection risk in wild pigs was positively correlated with humidity and IAV infection trends in domestic swine and humans, and did not show wave-like spatial spread of infection among states, nor more similar levels of infection risk among states with more similar meteorological conditions. Effects of host sex on IAV infection risk in wild pigs were generally not significant. Because most of the variation in infection risk was explained by state-level factors or infection risk at long-distances, our results suggested that predicting IAV infection risk in wild pigs is complicated by local ecological factors and potentially long-distance translocation of infection. In addition to revealing factors of IAV infection risk in wild pigs, our framework is broadly applicable for quantifying risk factors of disease transmission using opportunistic serosurveillance sampling, a common methodology in wildlife disease surveillance. Future research on the factors that determine individual-level antibody kinetics will facilitate the design of serosurveillance systems that can extract more accurate estimates of time-varying disease risk from quantitative antibody data

Effective Dose and Persistence of Rhodamine-B in Wild Pig Vibrissae

As a result of substantial ecological and economic damage attributed to wild pigs (Sus scrofa), there is international interest in using pharmaceutical baits to control populations. To assess the efficacy and specificity of baiting programs, chemical biomarkers can be used to evaluate uptake of pharmaceutical baits. Rhodamine B (RB) is known to be an effective biomarker in wild pigs. However, significant data gaps exist regarding the minimum effective dosage and persistence of RB in wild pigs. We used a controlled doubleblind study experiment conducted in spring of 2014 on the Savannah River Site, Aiken, South Carolina, USA, wherein we administered a one-time dose of RB at 3 treatment levels (5 mg/kg, 15mg/kg, or 30 mg/kg) to 15 captive pigs, with 5 pigs/treatment group to investigate persistence of RB. Facial vibrissae were collected pre-RB ingestion as a control and every 2 weeks post-RB ingestion for 12 weeks. We examined samples for RB presence and used a generalized linear mixed model (GLMM) to determine the influence of treatment dose on persistence of RB. Additionally, we measured distance moved by the RB mark away from the vibrissae root and used a GLMM to assess movement rates of RB bands along growing vibrissae. We found consistently greater persistence of RB in the 15- and 30-mg/kg treatments across the sampling period. A significant, positive movement trend in RB bands was observed within the 15mg/kg and 30 mg/kg groups. Based on our results, a 15 mg/kg dosage can be considered a minimum effective dose for wild pigs and will reliably produce a detectable RB mark up to and likely beyond 12 weeks after ingestion