Animal Health Research Reviews - Current Issue

Volume 9 Issue 01

Sat, 31 May 2008 23:00:00 GMT

Animal Health Research Reviews, Volume 9 Issue 01

Animal Health Research Reviews provides an international forum for the publication of reviews and commentaries on all aspects of animal health. Papers include in-depth analyses and broader overviews of all facets of health and science in both domestic and wild animals. Major subject areas include physiology and pharmacology, parasitology, bacteriology, food and environmental safety, epidemiology and virology. The journal will be of interest to researchers involved in animal health, parasitologists, food safety experts and academics interested in all aspects of animal production and welfare.

Frequentist and Bayesian approaches to prevalence estimation using examples from Johne's disease

Review Articles
Locksley L. McV. Messam, Adam J. Branscum, Michael T. Collins, Ian A. Gardner,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 1-23

Abstract
Although frequentist approaches to prevalence estimation are simple to apply, there are circumstances where it is difficult to satisfy assumptions of asymptotic normality and nonsensical point estimates (greater than 1 or less than 0) may result. This is particularly true when sample sizes are small, test prevalences are low and imperfect sensitivity and specificity of diagnostic tests need to be incorporated into calculations of true prevalence. Bayesian approaches offer several advantages including direct computation of range-respecting interval estimates (e.g. intervals between 0 and 1 for prevalence) without the requirement of transformations or large-sample approximations. They also allow direct probabilistic interpretation, and the flexibility to model in a straightforward manner the probability of zero prevalence. In this review, we present frequentist and Bayesian methods for animal- and herd-level true prevalence estimation based on individual and pooled samples. We provide statistical methods for detecting differences between population prevalence and frequentist methods for sample size and power calculations. All examples are motivated using Mycobacterium avium subspecies paratuberculosis infection and we provide WinBUGS code for all examples of Bayesian estimation.

Interactions between commensal bacteria and the gut-associated immune system of the chicken

Review Articles
Jennifer T. Brisbin, Joshua Gong, Shayan Sharif,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 101-110

Abstract
The chicken gut-associated lymphoid tissue is made up of a number of tissues and cells that are responsible for generating mucosal immune responses and maintaining intestinal homeostasis. The normal chicken microbiota also contributes to this via the ability to activate both innate defense mechanisms and adaptive immune responses. If left uncontrolled, immune activation in response to the normal microbiota would pose a risk of excessive inflammation and intestinal damage. Therefore, it is important that immune responses to the normal microbiota be under strict regulatory control. Through studies of mammals, it has been established that the mucosal immune system has specialized regulatory and anti-inflammatory mechanisms for eliminating or tolerating the normal microbiota. The mechanisms that exist in the chicken to control host responses to the normal microbiota, although assumed to be similar to that of mammals, have not yet been fully described. This review summarizes what is currently known about the host response to the intestinal microbiota, particularly in the chicken.

Actinobacillus pleuropneumoniae vaccines: from bacterins to new insights into vaccination strategies

Review Articles
Mahendrasingh Ramjeet, Vincent Deslandes, Julien Gouré, Mario Jacques,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 25-45

Abstract
With the growing emergence of antibiotic resistance and rising consumer demands concerning food safety, vaccination to prevent bacterial infections is of increasing relevance. Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, a respiratory disease leading to severe economic losses in the swine industry. Despite all the research and trials that were performed with A. pleuropneumoniae vaccination in the past, a safe vaccine that offers complete protection against all serotypes has yet not reached the market. However, recent advances made in the identification of new potential vaccine candidates and in the targeting of specific immune responses, give encouraging vaccination perspectives. Here, we review past and current knowledge on A. pleuropneumoniae vaccines as well as the newly available genomic tools and vaccination strategies that could be useful in the design of an efficient vaccine against A. pleuropneumoniae infection.

Antigen-independent priming: a transitional response of bovine γδ T-cells to infection

Review Articles
Mark A. Jutila, Jeff Holderness, Jill C. Graff, Jodi F. Hedges,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 47-57

Abstract
Analysis of global gene expression in immune cells has provided unique insights into immune system function and response to infection. Recently, we applied microarray and serial analysis of gene expression (SAGE) techniques to the study of T-cell function in humans and cattle. The intent of this review is to summarize the knowledge gained since our original comprehensive studies of bovine T-cell subsets. More recently, we have characterized the effects of mucosal infection or treatment with microbial products or mitogens on gene expression patterns in sorted and T-cells. These studies provided new insights into the function of bovine T-cells and led to a model in which response to pathogen-associated molecular patterns (PAMPs) induces of T-cells, resulting in more robust responses to downstream cytokine and/or antigen signals. PAMP primed T-cells are defined by up-regulation of a select number of cytokines, including MIP1 , and by antigens such as surface IL2 receptor ) and CD69, in the absence of a prototypic marker for an activated T-cell, IFN- -glucan are effective T-cell priming agents, but the most potent antigen-independent priming agonists defined to date are condensed oligomeric tannins produced by some plants.

Comparative antiviral and proviral factors in semen and vaccines for preventing viral dissemination from the male reproductive tract and semen

Review Articles
Jane Christopher-Hennings, Eric A. Nelson, Gary C. Althouse, Joan Lunney,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 59-69

Abstract
Many animal and human viruses are disseminated via semen, but there is little information on how to measure and stimulate protective antiviral immunity in the male reproductive tract and semen. This information is important since successful vaccination through the stimulation of protective immune responses could be a mechanism to prevent viral contamination of semen and subsequent wide spread viral dissemination. Even control of the infection by shortening the duration of viral shedding and lowering the viral load in semen would lessen the chances of viral dissemination through this route. This review will highlight the current knowledge of immunity in the male reproductive tract and summarize as well as factors in semen such as cytokines, cells, antibodies, antimicrobial peptides, enzymes, hormones and growth factors. These factors must provide a fine balance between in semen needed to protect sperm viability and to prevent pathogen contamination. The review will also suggest continuing challenges to researchers for preventing viral dissemination via semen and propose a large animal model for continued research in this important area.

Transmission dynamics and changing epidemiology of West Nile virus

Review Articles
Bradley J. Blitvich,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 71-86

Abstract
West Nile virus (WNV) is a flavivirus that is maintained in a bird mosquito transmission cycle. Humans, horses and other non-avian vertebrates are usually incidental hosts, but evidence is accumulating that this might not always be the case. Historically, WNV has been associated with asymptomatic infections and sporadic disease outbreaks in humans and horses in Africa, Europe, Asia and Australia. However, since 1994, the virus has caused frequent outbreaks of severe neuroinvasive disease in humans and horses in Europe and the Mediterranean Basin. In 1999, WNV underwent a dramatic expansion of its geographic range, and was reported for the first time in the Western Hemisphere during an outbreak of human and equine encephalitis in New York City. The outbreak was accompanied by extensive and unprecedented avian mortality. Since then, WNV has dispersed across the Western Hemisphere and is now found throughout the USA, Canada, Mexico and the Caribbean, and parts of Central and South America. WNV has been responsible for 27,000 human cases, 25,000 equine cases and hundreds of thousands of avian deaths in the USA but, surprisingly, there have been only sparse reports of WNV disease in vertebrates in the Caribbean and Latin America. This review summarizes our current understanding of WNV with particular emphasis on its transmission dynamics and changing epidemiology.

Sickness behavior, its mechanisms and significance

Review Articles
Ian Tizard,
Animal Health Research Reviews, Volume 9 Issue 01 , pp 87-99

Abstract
Recent studies have begun to clarify the pathogenesis of sickness behavior. Cytokines released by macrophages, dendritic cells and mast cells act on the brain to trigger behavioral changes in infected animals. The major cytokines, interleukin-1, tumor necrosis factor alpha, and others, all act on the hypothalamus to provoke alterations in the normal homeostatic condition. These include elevated body temperature, increased sleep, and loss of appetite as well as major alterations in lipid and protein metabolism leading to significant weight loss. Some of these changes are clearly directed towards enhancing the normal immune responses. The benefits of others such as appetite loss are unclear. It is also important to recognize that other animals may recognize sickness behavior as a sign of weakness and mark the victim out for targeting by predators. As a result, some prey species may work very hard to mask their sickness, a response that serves to complicate veterinary diagnosis.