The different ovine production and breeding systems share the cornerstone of keeping a good body condition to ensure adequate productivity. Several infectious and parasitic disorders have detrimental effects on weight gains and may lead to emaciation. Flock health management procedures are aimed to prevent such conditions. Nutritional management is equally important to guarantee adequate body condition. Persistent bouts of low ruminal pH due to excess concentrate in the diet may lead to subacute ruminal acidosis. Pre-stomach motility disorders may also lead to ill-thrift and emaciation. An adequate mineral supplementation is key to prevent the effects of copper, selenium, and other micronutrients deprivation, which may include, among others, loss of condition. This review elaborates on the clinico-pathologic, diagnostic, and therapeutic aspects of some of these conditions, and highlights the necessity of considering them as contributors to states of wasting in sheep flocks.

Enteritis, colitis, and enterocolitis are considered some of the most common causes of disease and death in horses. Determining the etiology of these conditions is challenging, among other reasons because different causes produce similar clinical signs and lesions, and also because some agents of colitis can be present in the intestine of normal animals. We review here the main bacterial and viral causes of enterocolitis of horses, including Salmonella spp., Clostridium perfringens type A NetF-positive, C. perfringens type C, Clostridioides difficile , Clostridium piliforme , Paeniclostridium sordellii , other clostridia, Rhodococcus equi , Neorickettsia risticii , Lawsonia intracellularis , equine rotavirus, and equine coronavirus. Diarrhea and colic are the hallmark clinical signs of colitis and enterocolitis, and the majority of these conditions are characterized by necrotizing changes in the mucosa of the small intestine, colon, cecum, or in a combination of these organs. The presumptive diagnosis is based on clinical, gross, and microscopic findings, and confirmed by detection of some of the agents and/or their toxins in the intestinal content or feces.

The clostridial diseases of horses can be divided into three major groups: enteric/enterotoxic, histotoxic, and neurotoxic. The main enteric/enterotoxic diseases include those produced by Clostridium perfringens type C and Clostridioides difficile, both of which are characterized by enterocolitis. The main histotoxic diseases are gas gangrene, Tyzzer disease, and infectious necrotic hepatitis. Gas gangrene is produced by one or more of the following microorganisms: C. perfringens type A, Clostridium septicum, Paeniclostridium sordellii, and Clostridium novyi type A, and it is characterized by necrotizing cellulitis and/or myositis. Tyzzer disease is produced by Clostridium piliforme and is mainly characterized by multifocal necrotizing hepatitis. Infectious necrotic hepatitis is produced by Clostridium novyi type B and is characterized by focal necrotizing hepatitis. The main neurotoxic clostridial diseases are tetanus and botulism, which are produced by Clostridium tetani and Clostridium botulinum, respectively. Tetanus is characterized by spastic paralysis and botulism by flaccid paralysis. Neither disease present with specific gross or microscopic lesions. The pathogenesis of clostridial diseases involves the production of toxins. Confirming a diagnosis of some of the clostridial diseases of horses is sometimes difficult, mainly because some agents can be present in tissues of normal animals. This paper reviews the main clostridial diseases of horses.

Streptococcus iniae is a re-emerging bacterial pathogen in freshwater and marine aquaculture worldwide. There are no commercial vaccines available for S. iniae in the United States, and autogenous vaccines are restricted to inactivated whole-cell preparations with limited protection against heterogenous strains. Live-attenuated vaccines (LAV) represent an advantageous alternative to these bacterins, as they induce robust cellular and humoral immunity, and may provide longer lasting protection through less stressful routes of administration. We investigated whether accumulation of mutations in S. iniae by serial passage in the presence of rifampin can generate immunogenic LAV conferring protection against challenge with heterologous wild-type (WT) S. iniae strains in Nile tilapia (Oreochromis niloticus). Three lineages of rifampin-resistant S. iniae strains were generated from three genetically distinct parent strains (n = 9) by multiple passages in increments of Rifamycin SV sodium salt. Growth in liquid media, extent of capsulation, antimicrobial susceptibility, survival in Nile tilapia whole blood, and cytotoxicity in an O. mossambicus endothelial cell line were compared between the passaged and WT strains. Nile tilapia challenges were used to assess strain virulence, generation of anti-S. iniae IgM, and the protection conferred by LAV candidates against virulent S. iniae. Rifampin-resistant strains demonstrated changes in growth rate and cytotoxicity in endothelial cells, as well as significant reductions in whole blood survival (p < 0.05). Selected strains also showed attenuated virulence in the Nile tilapia challenge model, and anti-S. iniae IgM generated against these strains demonstrated cross-reactivity against heterologous bacteria. Immunization by intracoelomic injection induced protection against a virulent WT strain of S. iniae, with relative percent survival up to 95.05%.

Rabbit hemorrhagic disease virus 2/genotype GI.2 (RHDV2/GI.2; Caliciviridae, Lagovirus) causes a highly contagious disease with hepatic necrosis and disseminated intravascular coagulation in several Leporidae species. RHDV2 was first detected in European rabbits ( Oryctolagus cuniculus) in France in 2010 and has since spread widely. We gather here data on viral detections reported in various countries and affected species, and discuss pathology, genetic differences, and novel diagnostic aspects. RHDV2 has been detected almost globally, with cases reported in Europe, Africa, Oceania, Asia, and North America as of 2023. Since 2020, large scale outbreaks have occurred in the United States and Mexico and, at the same time, cases have been reported for the first time in previously unaffected countries, such as China, Japan, Singapore, and South Africa, among others. Detections have been notified in domestic and wild European rabbits, hares and jackrabbits ( Lepus spp.), several species of cottontail and brush rabbits ( Sylvilagus spp.), pygmy rabbits ( Brachylagus idahoensis), and red rock rabbits ( Pronolagus spp.). RHDV2 has also been detected in a few non-lagomorph species. Detection of RHDV2 causing RHD in Sylvilagus spp. and Leporidae species other than those in the genera Oryctolagus and Lepus is very novel. The global spread of this fast-evolving RNA virus into previously unexploited geographic areas increases the likelihood of host range expansion as new species are exposed; animals may also be infected by nonpathogenic caliciviruses that are disseminated by almost all species, and with which genetic recombination may occur.

Reproductive failure represents an important cause of economic loss for the equine industry. We reviewed the cases of equine abortion and stillbirth submitted to the California Animal Health and Food Safety Laboratory System, University of California–Davis from 1990 to 2022. A total of 1,774 cases were reviewed. A confirmed cause of abortion was determined in 29.2% of the cases. Abortion or stillbirth was attributed to infectious agents in 18.7% of the cases, with Streptococcus spp., equine herpesvirus 1, and Leptospira spp. being the most prevalent. Noninfectious causes of abortion were established in 10.5% of the cases, with umbilical cord torsion being the most common. In 70.8% of the cases, a definitive cause of abortion could not be established. Our study demonstrated the difficulties in establishing an etiologic diagnosis, even when following a standard diagnostic work-up. New diagnostic approaches are needed to improve the likelihood of reaching a final diagnosis in cases of equine abortion and stillbirth.