Wooden breast (WB) myopathy of broiler chickens is a myodegenerative disease of an unknown etiology and is macroscopically characterized by a hardened consistency of the pectoralis major muscle. Our aim was to describe the development and morphology of WB over the growth period in broilers. Additionally, the effect of restricted dietary selenium on the occurrence of WB was examined by allocating the birds in 2 dietary groups: restricted and conventional level of selenium. The experiment included 240 male broilers that were euthanized at ages of 10, 18, 24, 35, 38, or 42 days and evaluated for WB based on abnormal hardness of the pectoralis major muscle. The severity and the distribution of the lesion and presence of white striping were recorded. The first WB cases were seen at 18 days; 13/47 birds (28%) were affected and the majority exhibited a mild focal lesion. In subsequent age groups the WB prevalence varied between 48% and 73% and the lesion was usually diffuse and markedly firm. White striping often coexisted with WB. Histological evaluation performed on 111 cases revealed a significant association of myodegeneration and lymphocytic vasculitis with WB. Vasculitis and perivascular cell infiltration were restricted to the veins. Restricted dietary selenium did not affect the occurrence of WB ( P = .44). Our results indicate that WB starts focally and spreads to form a diffuse and more severe lesion.

In wooden breast myopathy (WBM) of broiler chickens, the pectoralis major muscles show abnormally hard consistency and microscopical myodegeneration of unknown aetiology. To date, previous studies have focused primarily on chronic WBM and ultrastructural descriptions of early WBM are lacking. The aim of this study was to elucidate the pathogenesis of WBM by light microscopical morphometry of vessel density and the ultrastructural description of early WBM changes with transmission electron microscopy. The pectoral vessel density was compared between unaffected chickens (n = 14) and two areas of focal WBM in affected chickens (n = 14). The transverse myofibre area per vessel was highest in the unaffected area of muscle from cases of focal WBM, significantly higher (P = 0.01) than in macroscopically unaffected tissue, indicating that relatively decreased blood supply may trigger the development of WBM. The ultrastructural study included unaffected chickens (n = 3), two areas of focal WBM from affected chickens (n = 3) and areas of diffuse WBM from affected chickens (n = 3). The morphologically least affected myofibres within the WBM lesion areas in light microscopy exhibited ultrastructural changes of increased sarcoplasmic reticulum diameter and mitochondrial hyperplasia. Such changes originate typically from osmotic imbalance, for which the most likely aetiologies in WBM include tissue hypoxia or myodegeneration of the surrounding myofibres. The findings suggest that a relative reduction of blood supply in the major pectoral muscle occurs in the early phase of WBM, which may be linked to the ultrastructural changes of osmotic imbalance.

Although human infections caused by Trichinella sp. have not been reported in Finland for several decades and Trichinella sp. infection in pork has become virtually extinct in the last decade, sylvatic Trichinella spp. infection is still highly prevalent in Finland. Muscle digestion of 2,483 carnivorous wild animals from 9 host species during 1999-2005 showed 617 positive animals (24.8%). Molecular identification from 328 larval isolates revealed 4 different endemic Trichinella species, i.e., T. nativa, T. spiralis, T. britovi, and T. pseudospiralis. Seven percent of the infected animals carried mixed infections. Trichinella nativa was the most common species (74%), but T. spiralis was identified in 12%, T. britovi in 6%, and T. pseudospiralis in 1% of the animals. Host species showed different sample prevalence and Trichinella species distribution. Geographical distribution also varied, with the southern part of the country having significantly higher percentages than the northern part. Infection density was dependent on both the infecting Trichinella species and the host species. Trichinella spiralis was discovered in areas with no known domestic infection cases, indicating that it can also occur in the sylvatic cycle. Raccoon dogs and red foxes are the most important reservoir animals for T. spiralis , as well as for the sylvatic Trichinella species in Finland.

A horse in Finland exhibited generalized granulomatous inflammation and severe proliferative dermatitis. After euthanization, we detected poxvirus DNA from a skin lesion sample. The virus sequence grouped with parapoxviruses, closely resembling a novel poxvirus detected in humans in the United States after horse contact. Our findings indicate horses may be a reservoir for zoonotic parapoxvirus.

Mycobacteriosis caused by non-tuberculous mycobacteria (NTM) is a rising concern in human medicine both in immunocompromised and immunocompetent patients. In cats, mycobacteriosis caused by NTM is considered mostly to be a focal or dermal infection, with disseminated disease mostly caused by Mycobacterium avium. We describe three cases of disseminated mycobacteriosis in cats, caused by Mycobacterium malmoense, Mycobacterium branderi/shimoidei and M. avium, with no identified underlying immunosuppression. In all cases, extracellular mycobacteria were seen in the pulmonary epithelium, intestinal lumen and glomerular tufts, which could affect the shedding of the organism. The present study highlights the importance of mycobacteriosis as a differential even in immunocompetent animals. Considering the close relationship of owners and pets and the potential presence of free mycobacteria in secretions, cats should be considered as a possible environmental reservoir for mycobacteria.

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Rats are selective hosts for Trichinella nativa; infection levels in their muscles remain low when compared to Trichinella spiralis. To identify in which phase of the life cycle the selective responses take place, rats were infected perorally (p.o.) and intravenously (i.v.) with T. spiralis and T. nativa. Six rats were placed in each group; three rats served as uninfected controls. The infection intensities were examined 5 or 6 weeks after the infection. T. spiralis muscle larva burden was 57 times higher compared to that of T. nativa after p.o. inoculation (mean larvae per gram ± SD, 1,243 ± 378.9 vs. 22 ± 21.5). In i.v. inoculation, 12 times more T. spiralis larvae reached the muscle than with T. nativa. Also, in vitro newborn larva (NBL) production at day 6 postinfection was analyzed for parasites originating from both rat and mouse. The mean number of in vitro-produced NBL of rat-origin T. spiralis during 24 h was 70 (95 % CI, 65-75) and of T. nativa, 23 (95 % CI, 21-24). Intriguingly, this difference was less obvious with mouse-origin female Trichinella. NBL production of mouse origin T. spiralis was 57 (95 % CI, 51-62) and T. nativa, 29 (95 % CI, 26-31). Intestine histology at day 40 post p.o. infection, serological response, and weight dynamics were indistinguishable between the Trichinella species but differed from controls. Our results show that the defense against T. nativa is not solely enteral in rats but may partly be explained by different reproduction processes for the two Trichinella species in rat.

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