Experimental infections with Piscirickettsia salmonis via intraperitoneal (IP), oral (PO) and gill (GS) routes were compared, and the importance of physical contact in the horizontal transmission of this organism was investigated. Atlantic salmon, Salmo salar L., under‐yearling parr raised in fresh water were used in this study. Samples of liver, kidney, spleen, gill and brain were collected weekly for 5 weeks after challenge, and were examined using the indirect fluorescent‐antibody technique (IFAT). The pathogen was transmitted horizontally to fish with and without physical contact. However, transmission of P. salmonis occurred significantly more rapidly among fish with physical contact. Mortalities occurred in 50% of fish experimentally challenged with P. salmonis and their cohabitants. The estimates of the relative risk of dying demonstrated that fish challenged by the IP and GS routes had a significantly higher probability of dying than fish challenged by the PO route (P < 0.005). Contact cohabitants with infected fish had a higher probability of death than non‐contact cohabitants (P < 0.005). The sequential studying using IFAT indicated that a haematogenous pattern of infection occurred among fish infected by oral and gill routes, or by cohabitation. This was different from the capsular (serosal) infection pattern observed in intraperitoneally inoculated fish. Piscirickettsia salmonis was observed within the cytoplasm of leucocytes and renal tubules, the latter indicating that elimination of this pathogen through the urine may be possible. Aeromonas salmonicida was also detected (by IFAT) in some of the fish exposed to P. salmonis, suggesting that P. salmonis may cause immunosuppression, and thus, increase the susceptibility of the host to other pathogens.

No abstract

Diagnosis of copper toxicosis (CT) in Bedlington terriers by the quantitative and qualitative assessment of copper (Cu) in, and pathology of, biopsies has been largely superseded by a DNA-based assay which uses a microsatellite marker (C04107) linked to the CT disease allele. A retrospective study was conducted comprising 154 liver biopsies from Bedlington terriers with 22 matched DNA markers to compare the two methods in the diagnosis of CT. For the biopsy method, three categories (phenotypes) were identified based on analytical and morphological criteria: 'unaffected' in 83 samples (54 per cent), where Cu was much less than 400 microg/g, and there was an absence of visual Cu or liver damage; 'intermediate' in 18 samples (12 per cent), where Cu was less than 400 microg/g, and there was limited histochemical Cu and no/equivocal damage; and 'affected' in 53 samples (34 per cent), where Cu was greater than 400 microg/g, there was histochemical Cu and liver damage was poorly related to Cu content. In the DNA assay, which was used alone on unrelated individuals, the microsatellite marker failed to identify the CT status of any of the groups. Liver biopsy remains a reliable indicator of Cu accumulation and progressive liver disease in individual dogs. The microsatellite marker C04107 has a predictive value only when supported by a pedigree.

Young Fischer 344 rats are more susceptible than adults to copper-induced liver injury.

Abstract. Microsporidia have been recognized recently as opportunistic pathogens in acquired immunodeficiency syndrome patients. In an attempt to develop an animal model of enteric microsporidiosis, adult (5 to 6 months old) male Flemish Giant rabbits from a closed New York colony were administered 5 x 10 3,5 X 10 5 , and 5 x 10 7 Encephalitozoon cuniculi per rectum. Rabbits given 5 x 10 5 and 5 x 10 7 E. cuniculi had moderate granulomatous periportal infiltrates, characterized by the presence of numerous macrophages, epithelioid cells, and a few multinucleated giant cells, lymphocytes, and plasma cells. Inflammatory cells also were seen infiltrating the tunica adventitia and tunica media of hepatic portal veins and branches of the hepatic artery. This study demonstrates that administration of E. cuniculi per rectum to rabbits results in infection that is characterized by high frequency and severity of hepatic lesions.