Characterization of Cryptosporidium spp.--recent developments and future needs

Cryptosporidia, widely distributed protozoan parasites of vertebrates have recently attracted increasing interest due to several serious waterborne outbreaks, the life-threatening nature of infection in immunocompromised patients, and the realization of economic losses caused by these pathogens in livestock. Genetic polymorphism within Cryptosporidium spp. is being detected at a continuously growing rate, owing to the widespread use of modern molecular techniques. The aim of this paper is to review the current status of taxonomy, genotyping, molecular phylogeny, and characterization of cryptosporidia, and to highlight the need for polyphasic typing, i.e. an integrated approach comprising standardized morphologic, biologic, and molecular methods for describing Cryptosporidium species and isolates, and for establishing "virtual" reference strains.     

Histological lesions in vascular tissues of bovine herpes virus type 4-infected rabbits

The gamma-herpes virus bovine herpes virus type 4 (BoHV-4) is distributed worldwide in cattle populations with unknown pathogenicity. Bovine endothelial cells were recently shown to be susceptible to BoHV-4 infection in vitro and this virus accelerated the cholesterol-induced atherosclerotic process in rabbits. In this study, the in vivo effect of BoHV-4 on cardiovascular tissue was investigated by intravenous infection of rabbits fed a cholesterol free diet. Inflammatory lesions of vascular tissue in aortic and valvular endothelial cells, and smooth muscle cells were detected by H&E staining, PCR, IF, EM immunohistochemistry, while virus isolation was used to detect virus particles. Acute and chronic vasculitis, signs of chronic endocarditis, with mononuclear cell accumulation and a fresh thrombus was found. Herpes viruses have already been thought to initiate cardio-vascular disorders, now this paper shows that a bovine gamma-herpes virus could also be a causative agent of vascular lesions in mammals fed a normal diet. BoHV-4-infection of rabbits could serve as a useful animal model for research into virus-induced human cardio-vascular diseases.     

Bovine herpesvirus type 4: a special herpesvirus (review article)

This paper summarizes the history of and information on bovine herpesvirus type 4 (BoHV-4) from the first isolation to the most recent results. For almost twenty years BoHV-4 has been considered a typical herpes 'orphan' virus, which infects several species but causes no illness. The latest experiments revealed the close relationship of this virus with the immune system and other tissues. The virus was even considered as a possible candidate for a vector vaccine. BoHV-4 as a strange herpesvirus has several features which are not characteristic of other herpesviruses, such as several latency sites, persistence in serum, dividing cells necessary for virus replication, and the wide host range. In addition to describing the main features of the virion, replication, clinical signs, nomenclature problems, this review intends to concentrate on the new and strange results coming out from several laboratories worldwide. It is also suggested that because the virus combines several properties of various herpesvirus subfamilies and because of its close relationship with the immune system, it may deserve further attention as a representative of a potentially new genus within the Gammaherpesvirinae subfamily.     

Genomic and Pathogenic Studies on a Glycoprotein E Variant Field Isolate of Bovine Herpesvirus 1

Glycoprotein E-negative (gE–) laboratory strains of bovine herpesvirus 1 (BHV-1) were recently introduced as novel marker vaccines, allowing serological discrimination between vaccinated and naturally infected animals on the basis of lack or presence of antibodies against gE epitopes. The applicability of this approach is based on the genetic stability of the gE. However, mutant field variants of BHV-1 with a variable response in anti-gE ELISA have been isolated. The molecular characterization of a gE variant field isolate (Salwa strain) is presented here. By comparing the gE nucleotide and amino acid sequences of the Salwa strain with those of the wild strain Jura, ten mutated bases were found in the gE strain of Salwa, six of which alter the amino acid sequence, leading to changes in five amino acids. Both strains caused respiratory disease in experimentally infected calves, but Salwa generated slightly milder signs. Both viruses were excreted in nasal and ocular discharges, and were reactivated by dexamethasone treatment. In conclusion, the rather close similarities observed in the gE gene structure and pathogenicity features of the gE mutant and of the wild strain of BHV-1 confirm the genetic stability of gE. The findings indicate that the Salwa isolate is virulent, but less virulent than wild strains. Our data support the use of gE-negative marker vaccines in eradication programmes.     

Human exposure to mercury may decrease as acidic deposition increases

It has been hypothesized that human mercury (Hg) exposure via fish consumption will increase with increasing acidic deposition. Specifically, acidic deposition leads to reduced lake pH and alkalinity, and increased sulphate ion concentration ([SO₄ ^2?]), which in turn should cause increased Hg levels in fish, ultimately resulting in increased human Hg exposure via fish consumption. Our empirical test of this hypothesis found it to be false. We specifically examined Hg levels in the hair of Ontario Amerindians, who are known consumers of fish from lakes across the province, and observed a weak negative association with increasing sulphate deposition. An examination of Hg levels in lake trout, northern pike and walleye, three freshwater fish species commonly consumed by Ontario Amerindians, found a similar weak negative association with increasing sulphate deposition. Further analysis of these fish data found that fish [Hg] was most significantly (positively) associated with lake water concentrations of dissolved organic carbon (DOC), not pH, alkalinity or [SO₄ ^2?]. Lake DOC levels are lower in regions of greater acidic deposition. We propose an alternate hypothesis whereby human Hg exposure declines with increasing acidic deposition. In particular, we propose that increasing sulphate deposition leads to reduced lake DOC levels, which in turn leads to lower Hg in fish, ultimately reducing human Hg exposure via fish consumption.     

The efficacy of acetamide for the treatment of experimental Dichapetalum cymosum (gifblaar) poisoning in sheep

High mortality of livestock is caused annually by the plant, Dichapetalum cymosum (gifblaar), in the Northern Transvaal. So far no therapeutic measures have been developed for the prevention or treatment of this poisoning. In this presentation, the efficacy of acetamide as therapy for experimental gifblaar poisoning was tested in 18 sheep. When 2.5-5 g/kg of acetamide was dosed to sheep at various intervals before and sometimes after the administration of 5 g/kg of gifblaar, 1 out of 5 survived, compared with 0 out of 2 controls. Dosing of 2 g/kg of acetamide before and/or simultaneously with or after 1 g/kg gifblaar prevented mortality as 5 out of 5 treated sheep survived compared with none of the 5 controls. The experiments indicate that acetamide has demonstrable therapeutic value as an antidote for the prevention of experimental gifblaar poisoning in sheep. Further investigations should determine the feasibility and applicability of these findings under field conditions in sheep and cattle.     

Chronic lesions in geese photosensitized by Ammi majus.

Chronic lesions of the beak, footweb, and eye of geese photosensitized by the comsumption of Ammi majus (L.) are described, 7 weeks after the acute symptoms commenced. Sixty-four (48%) of the 133 birds in the flock showed various degrees of abnormality. All affected birds had stunting of the upper beak and cicatrization and thickening of the footweb. Eighty-nine percent of the affected birds showed ocular involvement, comprising chemosis, blepharoconjunctivitis, keratitis, symblepharon, ankyloblepharon, cicatricial ectropium, and mydriasis.     

The effect of tiamulin administered by different routes and at different ages to turkeys receiving monensin in their feed

Healthy turkeys receiving 80 ppm monensin in their feed were injected at 26, 40 and 61 days of age with tiamulin at dosages of 12.5 and 25 mg/kg body weight. The aim of the study was to develop a regime for medicating with tiamulin turkeys receiving monensin in their feed, and which would circumvent the known toxicity created by the simultaneous administration of the two drugs. One injection of 12.5 mg/kg tiamulin up to the age of 61 days or 2 injections of 12.5 mg/kg tiamulin up to 40 days of age caused no mortality or adverse reaction.     

Detection of bovine herpesvirus 4 in CD11b+ leukocytes of experimentally infected rabbits

The presence and numbers of bovine herpesvirus 4 (BoHV-4) infected CD11b+ leukocytes were investigated during experimental infections of New Zealand White rabbits by Fluorescence Activated Cell Sorter (FACS) analysis. Peripheral blood leukocytes (PBL) were collected every second day, and the cells were stained with phycoerythrin-labelled CD11b-specific mouse monoclonal antibody and fluorescein-conjugated bovine herpesvirus 4-specific mouse monoclonal antibody. The numbers of double-stained cells from PBLs of the control and inoculated groups were measured and compared in FACSTREK analyser. Double-stained cells were detected in the virus-inoculated group on postinoculation days (PID) 2-5 and 9-12. The results indicated that CD11b+ PBLs were permissive for BoHV-4 infection, and are probably the main reservoir of the virus during the latent period. The data did not indicate production of infectious viral particles, but virus-specific proteins were expressed on the surface of CD11b+ cells. The two waves of double-stained cells gave similar results to the PCR assays from serum samples, which showed the presence of viral DNA in the serum on the same days when virus-infected CD11b cells were also present. Productive BoHV-4 infection of mast cells or undifferentiated leukocytes in the bone marrow and the antiviral immune response might be responsible for this periodic appearance of the virus in CD11b+ PBLs and in the serum. The paper provides evidence that CD11b+ PBLs are the main target cell populations in the blood for BoHV-4.     

Tick-borne encephalitis epidemic in Hungary 1951–2021: The story and lessons learned

The authors analysed epidemiological data of the Hungarian tick-borne encephalitis epidemic from the past seven decades. A total of 911 meningitis serosa cases were described from 1930-1950 s by local hospital physicians, indicating that the virus had been present in the country decades before its official identification in 1952. The virus spread freely in the 1950s–1960s, occupying almost all habitats where ticks occurred in large numbers. The increasing number of cases drove authorities to classify this illness as a notifiable disease in 1977 and to organize the first measures to stop the epidemic. Statistical analysis revealed that the large-scale vaccination launched from the 1990s was responsible for the sharp decrease in the number of human cases from 1997. A significant negative correlation was found between the number of vaccine doses sold and human cases 6 years later. The TBEV endemic area covers 16.57% of the territory and 16.65% of the population of the country. In the last 10 years, 186,000 vaccine doses/year in average were enough to keep the incidence of human TBEV infections between 0.45 and 0.06/100,000 persons. A 20-year-long study found evidence for easing clinical signs in TBEV-infected hospitalized patients. Statistics found a sharp decrease in the number of samples sent for TBEV diagnosis after 1989. Male dominance of patients was characteristic of the epidemics since the 1940s, but now analysis of detailed data from the 1981–2021 period (60.5%–87.5%) proved the statistical significance of this dominance. Obviously, the voluntary vaccination programme was the tool which broke the spread of the epidemic. Widespread public awareness of the disease and the tick vector, probable evolutionary spread of less pathogenic virus strains supplemented with the vaccination campaign led to a negligible level of human TBE cases in Hungary in the last years.