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Porcine reproductive and respiratory syndrome virus (PRRSV) displays notorious genetic, antigenic, and clinical variability. Little is known, however, about the nature and extent of viral variation present within naturally infected animals. By amplifying and cloning the open reading frame 5 gene from tonsils of naturally infected swine, and by sequencing individual clones, we characterized viral diversity in nine animals from two farms. All animals harbored multiple PRRSV variants at both the nucleic and the amino acid levels. Structural variation and rates of synonymous and nonsynonymous nucleotide substitution were no different within known epitopes than elsewhere. Analysis of molecular variance indicated that differences between farms, among animals within farms, and within individual animals accounted for 92.94, 3.84, and 3.22% of the total viral genetic variability observed, respectively. PRRSV exists during natural infection as a quasispecies distribution of related genotypes. Positive natural selection for immune evasiveness does not appear to maintain this diversity.

Neospora caninum infection is a common cause of bovine abortion. One method by which cattle can acquire infection is through ingestion of oocysts; however, this has not yet been proved to cause transplacental infection or abortion. In this study, 19 cows, pregnant between 70 and 176 days, were administered 1500 to 115,000 oocysts through an esophageal tube. Seventeen of the cows became seropositive, indicating acquisition of infection, whereas 8 negative control cows remained seronegative (P < 0.001). Offspring were examined using serology, histology, immunohistochemistry, parasite isolation, and polymerase chain reaction (PCR). Six offspring were infected and 1 of them was aborted. The aborted fetus had typical lesions and positive immunohistochemistry and PCR for N. caninum. All 6 cows with infected offspring had continuously rising antibody titers, whereas 10 of 11 infected cows with uninfected offspring had falling titers after an early apex. The risk of transplacental transmission was increased by later exposure times during gestation and by the dose of oocysts (P < 0.01 for the 2 combined variables). The lowest dose of oocysts, when administered after the 160th day of gestation, caused transplacental infection in 1 of 2 animals. This study demonstrates that infection with N. caninum oocysts can cause transplacental transmission and abortion in cattle.

Assessing Animal WelfareWhen evaluating how housing affects the welfare of pregnant sows, it is important to be clear about what is meant by animal welfare. Commonly expressed concerns include the following: 1) animals should function well in the sense of being healthy and thriving; 2) animals should feel well, especially by prevention of serious pain, hunger, fear, and other forms of suffering; and 3) animals should be able to live in a manner consistent with the nature of their species. 1 Task Force members recognized that scientists, including veterinarians, approach animal welfare from different viewpoints and attribute various degrees of importance to each of these concerns on the basis of their education, training, experience, and personal values and the perspectives, morals, and ethical constructs of the society in which they live and work. [2][3][4][5] The ways in which other segments of society interpret animal welfare are likewise diverse. A study 6 conducted in The Netherlands found that producers tended to believe that health and normal biological function were evidence of good animal welfare, whereas consumers tended to focus on the animal' s ability to live a reasonably natural life. A sampling of quotations by ethicists and social critics identified suffering and other affective states as central concerns. 7 Although the degree of importance attributed to each of these elements may vary, Task Force members agreed that no assessment of animal welfare is complete unless all elements are considered. It is not satisfactory, for example, to judge the welfare of an animal on the basis of its physical health without regard for whether it is suffering or frustrated or to conclude that an animal that can engage in species-typical behavior has a good state of welfare without also carefully evaluating its health and physiologic function. In recognition of the need for a comprehensive approach, physiologic function, behavior, physical health, and production indices were used to evaluate the effects and appropriateness of the use of gestation stalls, compared with other systems, for housing pregnant sows. Because ethical perspectives may affect how scientific data are

Evidence that a strong CMI response was correlated with protection against clinical PRRS was detected in 3 of 4 farms. However, farms and sows within farms varied considerably in their immune responsiveness and in the degree to which they were protected clinically. Increasing cell-mediated immunity within infected herds has the potential to decrease clinical reproductive disease, but only if the sources of intra- and interfarm variation in the intensity of cell-mediated immunity to PRRS virus can be identified.

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Results indicated that oral administration of spinosad at 300 mg/kg alone or in combination with MBO at doses up to 10 mg/kg did not cause signs of AVM-MB toxicosis in AVM-MB-sensitive dogs with the MDR1 gene mutation.

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