Correlation of virus replication in tissues with histologic lesions in Atlantic salmon experimentally infected with infectious salmon anemia virus.

We have studied the replication of virus in tissues and development of lesions associated with infectious salmon anemia virus (ISAV) infection in Atlantic salmon using in situ hybridization (ISH) with a riboprobe targeting ISAV RNA segment 7 messenger RNA. Fish were infected with three ISAV isolates (U5575-1, RPC-01-0593-1, Norway 810/9/99) and then euthanatized sequentially at 3, 6, 10, and 13 days postinoculation (dpi) and thereafter once a week for 8 weeks. Severe histopathologic lesions were observed in tissues from all groups beginning at the onset of mortality. The severe histopathologic lesions correlated with maximum intensity and frequency of ISH signals (P < 0.001). There was a strong association between the hybridization signals and severity of lesions in the liver, kidney, and heart (R = 0.81, 0.70, and 0.78, respectively; P < 0.001). The distribution of ISH signals indicated the presence of a viremia because signals were observed predominantly in individual blood cells and endothelial cells, and possibly hematopoietic cells of head kidney, but not in the necrotic hepatocytes and renal epithelium. Of the organs sampled, the heart was the first and last to show ISH signals, possibly because of increased activity of the endocardial endothelial cells and the underlining macrophages, which continuously trap and remove circulating virus, and therefore represents the best tissue sample for screening of suspected infected fish. On the basis of mortality, severity of lesions, and intensity and frequency of ISH signals, ISAV isolate Norway 810/9/99 was the most virulent and U5575-1 the least virulent isolate studied.

The failure of selenium supplementation to prevent copper-induced liver damage in Fischer 344 rats.

This study evaluates the ability of selenium (Se) supplementation to prevent experimental copper (Cu)-induced hepatocellular damage. Weanling male Fischer 344 rats were randomly assigned to groups of 15, 3 groups (A,B,C) were fed Cu-loaded diets (containing 2000 microg/g copper, added as CuSO4) and different levels of Se (added as Na2SeO3 x 5H2O) as follows: A) Cu-loaded/Se adequate diet (0.4 microg/g Se, fed basis); B) Cu-loaded/Se-supplemented diet (2 microg/g Se); and C) Cu-loaded/Se-deficient diet (< 0.2 microg/g). Three additional groups (D,E,F) were fed diets containing adequate levels of Cu (14 microg/g Cu, fed basis) and different levels of Se as follows: D) Cu-adequate/Se-adequate diet; E) Cu-adequate/Se-supplemented diet (2 microg/g Se); and F) Cu-adequate/Se-deficient (< 0.2 microg/g) diet. After 4, 8, and 12 weeks on the experimental diets, liver samples were processed for histology, histochemistry, metal analysis, glutathione peroxidase (GSH-Px) measurement, and quantification of malondialdehyde (MDA). Morphologic changes characteristic of Cu-associated hepatitis, without an increase in hepatic MDA levels, were seen in all Cu-loaded rats in each sampling. Similar changes occurred in rats fed Se-adequate, Se-supplemented and Se-deficient diets. This study demonstrates that Fischer 344 rats fed 2000 microg/g Cu develop morphologic changes due to Cu toxicity without evidence of lipid peroxidation. Furthermore, Se supplementation does not result in protection against Cu-induced liver injury.

Morphological and biochemical assessment of the liver response to excess dietary copper in Fischer 344 rats.

The aim of this study was to determine the amount of excess dietary copper (Cu) necessary to experimentally induce liver lesions characteristic of Cu-associated disease in Fischer 344 rats. Male weanling Fischer 344 rats of uniform age were divided into 6 groups (n = 5) and fed a rodent diet containing 18 (control), 750, 1000, 1250, 1500, and 2000 microg/g Cu added as CuSO4. Rats were euthanized after 3 months on the experimental diets and their livers processed for histology, histochemistry, Cu analysis (by atomic absorption spectrophotometry), and quantification of malondialdehyde (MDA) by the thiobarbituric acid reaction. Hepatic Cu levels were significantly higher (P < 0.01) in rats receiving over 1000 microg/g Cu compared to the controls (means for each diet: control = 4.8 microg/g, 750 microg/g Cu = 39.6 microg/g, 1000 microg/g Cu = 111.2 microg/g, 1250 microg/g Cu = 389 microg/g, 1500 microg/g Cu = 509.4 microg/g, and 2000 microg/g Cu = 766 microg/g). Histological lesions increased gradually according to the level of dietary Cu. Significant morphologic changes (necrosis, portal inflammation, hyaline remnants) and reduced growth rate occurred in rats receiving over 1250 microg/g Cu. However, no significant differences were found for MDA levels between groups. The present study demonstrates that compared to other species, very high levels of excess dietary Cu are needed to induce significant liver injury in Fischer 344 rats. Increased MDA content was not detected in rats with morphologic evidence of liver damage, suggesting that lipid peroxidation may not play a major role in this model of Cu toxicity.

Congenital joint laxity and disproportionate dwarfism in a herd of beef cattle.

Three calves from a herd of beef cattle were examined because of disproportionate dwarfism and excessive extension of metacarpophalangeal and metatarsophalangeal joints. Abnormalities had been noticed at birth, 1 to 6 days earlier. A thorough herd investigation revealed that 16 calves born to 70 multiparous cows were affected during the calving season. The condition did not adversely affect calf survival. Affected calves had limbs that were disproportionally short, compared with their trunk size, and wide epiphyses of the femurs and humeri. Radiographic evaluation revealed incomplete maturation of carpal and tarsal bones and incomplete maturation and abnormal flaring of epiphyses of the short humeri and femurs. Histologic findings were consistent with chondrodystrophy. This disorder had not been seen in the herd in previous years and was traced to feeding of dry, spoiled silage to the dams during midgestation. Covering the silage prevented problems in the subsequent year.

Trypanosomosis and reproduction: II. Effect of Trypanosoma vivax infection on pregnancy and post-partum cyclicity in ewes.

The effect of infection with Trypanosoma vivax on pregnancy and post-partum cyclicity in ewes was investigated. Of the 5 ewes infected in the first trimester, 3 died without aborting and 2 after aborting. Intrauterine infection occurred in 2 of the foetuses removed at post mortem. Of the 5 infected in the third trimester, one ewe died without aborting, one lambed prematurely and 3 at term. Intrauterine infection occurred in one of the lambs born at term. None of the lambs were viable. The termination of pregnancy may be as a result of stress. The ewes infected in the third trimester commenced irregular cyclicity 13 to 23 days post partum.

Trypanosomosis and reproduction: I. Effect of Trypanosoma vivax infection on the oestrous cycle and fertility in the ewe.

Ten West African Dwarf ewes were inoculated with Trypanosoma vivax and, at varying intervals, treated subcuratively with diminazene aceturate to maintain the infection. Soon after infection all ewes had anoestrus for 40 to 96 days and 5 died by day 110 post infection. Compared to control animals, infected ewes had prolonged low levels of plasma progesterone until recovery or death. However, no gross or histological lesions were detected in the endocrine or reproductive organs. Of the survivors, the 5 that were aparasitaemic subsequently became pregnant and had normal gestations.

Role of the chancre in induction of immunity to tsetse-transmitted Trypanosoma (Nannomonas) congolense in goats.

Local skin reactions (chancres) developed in goats at the sites of deposition, by tsetse flies, of metacyclics of Trypanosoma congolense. The chancres developed much faster and were more pronounced when ten infected tsetse were allowed to feed on a spot as compared to only one fly per spot. The initial host cellular reaction in the chancre was predominantly polymorphonuclear, followed at the peak of development of the chancre by a predominantly lymphoblastic and plasmacytic reaction. Trypanosomes were found in various stages of division as well as degeneration in chancre biopsies taken at various days post-infection (p.i.). Most of the trypanosomes recovered from the chancre tissue fluid were found to bear the same variable surface glycoprotein (VSG) epitopes as the corresponding metacyclics for as long as 13 days p.i., as revealed by indirect immunofluorescence using mouse anti-metacyclic VSG hyperimmune sera and monoclonal antibodies. Immunization of goats with metacyclic trypanosomes, by exposure to infected tsetse bites followed by treatment of the infected goats on day 13 p.i., gave rise to the development of protection to homologous tsetse-transmitted challenge, whilst immunization by intravenous inoculation of the metacyclics did not induce such protection. Chancre formation would thus appear to be vital for the induction of comprehensive immune recognition of the metacyclic variable antigen repertoire deposited in the skin by infected tsetse, and hence development of protective immunity.

Fluid, electrolyte and haematological changes in experimental peste des petits ruminants virus infection in West African dwarf goats.

The changes in plasma volume, blood volume, erythrocyte indices, leucocyte indices and serum biochemical values during experimental pestes des petits ruminants (PPR) virus infection of West African dwarf goats (Fouta djallon) were investigated. There was a progressive decline of the plasma volume and serum sodium and potassium values in all the infected goats as from day 5 post-infection and this became quite marked between days 10 and 23 post-infection. The fall was severest in those animals which had diarrhoea. There were no significant changes in the chloride, bicarbonate, phosphate, urea, total protein and albumin values of the goats during the course of the diseases. Haemoconcentration and apparent polycythaemia in the early and terminal stages of the disease were associated with severe dehydration which characterized the infection. There was initial neutrophilic leucocytosis during the phase of fever followed by marked lymphopaenic leucopaenia which progressed terminally in most of the infected goats. The destructive effect of the virus on lymphocytes is suggested as a cause of lymphopaenia.

Correlation of humoral immune response with clinical presentation, pulmonary lesions and mortality patterns of goats experimentally infected with peste des petits ruminants virus.

The patterns of humoral immune response, measured by enzyme-linked immunosorbent assay and the development of clinical signs, pulmonary lesions and mortality patterns were studied in goats experimentally infected with peste des petits ruminants virus (PPRV) or Kata virus. It was possible to classify the animals into high and low responders according to the pattern of humoral immune response. The high responders had a prolonged, chronic infection characterized by a giant cell pneumonia which was sometimes complicated by bronchopneumonia. Such animals survived beyond 1 month. The low immune responders had a subacute or acute clinical presentation. In the former case, the animals developed an uncomplicated giant cell pneumonia and died within 1 month of infection. Those with the acute symptoms developed pulmonary congestion and oedema and succumbed to the infection in 1 week. The clinical and pathological response of goats to PPRV infection, and ultimately the outcome of the infection correlated well with the ability of the goats to mount specific antibodies to PPRV.

Reproductive disorders in African trypanosomiasis: a review.

Reproductive disorders are frequently seen in human beings and in animals infected with tsetse-transmitted (African)trypanosomiasis. The disorders include irregular menstrual (or oestrus) cycle, infertility, abortion and impotence. Intrauterine infections occasionally occur, resulting in still birth or neonatal mortality. The changes are essentially reversible after treatment, although recovery may take several months.

Ejaculate characteristics of sheep infected with Trypanosoma brucei and T vivax: changes caused by treatment with diminazene aceturate.

The effect of Trypanosoma brucei and T vivax on the ejaculate of sheep and the rate of recovery with diminazene aceturate treatment was investigated. Animals were made to ejaculate once a week before infection, during infection and after treatment. Parameters studied were semen volume, semen colour, sperm motility and concentration, percentage dead spermatozoa and sperm morphology. Both infections severely affected the quality of the ejaculate although in T vivax infection there was no appreciable change in semen volume and sperm concentration. There was a reduction in sperm motility and concentration, an increase in the percentage of dead spermatozoa and in abnormal sperm morphology. Treatment led to improvement in all parameters but recovery was faster in T vivax than in T brucei infection. Ejaculate with few primary abnormalities was not obtained until 19 weeks after treatment.

Characterization of Nigerian strains of Newcastle disease virus.

Newcastle disease virus was isolated from outbreaks of the disease in vaccinated and unvaccinated poultry flocks representing commercial and backyard farms in different parts of Nigeria. On characterization, all 12 isolates were found to be velogenic.

Delay in resolution of trypanosome-induced genital lesions in male rabbits infected with Trypanosoma brucei and treated with diminazene aceturate.

The effects of drug therapy on the resolution of the genital lesions accompanying systemic Trypanosoma brucei infection was investigated using male California White rabbits. Infected animals were treated with diminazene aceturate two to 13 days after the onset of gross scrotal lesions; they were killed at different intervals after treatment to determine the histological evidence of healing of the genital lesions. It was found that, although parasites disappeared soon after treatment, regeneration of seminiferous epithelium depended on the severity of the initial lesions. Only mildly afflicted rabbits had fully recovered within 141 days.