A comprehensive survey to document the presence of free-living amoebae was conducted along 58 km of James River, near Richmond, Virginia, USA. Sites included tidal and non-tidal freshwater areas, near 40 combined sewer outflows, three municipal wastewater treatment plant release sites, and thermal discharge from a coal-fired power plant. Amoebae were present on all collection dates, spring through autumn, and at all sites ( n=330). Five genera, Naegleria, Vannella, Acanthamoeba, Vahlkampfia, and Hartmannella were present in both the water column and sediment. The most common isolates from the water column were Naegleria and Vannella. Water conditions conducive to the presence of large quantities of fecal coliform bacteria were correlated with the prevalence of free-living amoebae. Some of the amoebae in this complex ecosystem can act as opportunistic pathogens, may play a role in diseases of aquatic organisms in this heavily urbanized river, and may present a risk to human health.

A positive correlation was found between genetic predisposition to diabetes in the mouse and susceptibility to group B Coxsackie virus in this host. Male mice of the inbred strain C57BL/Ks and the following genetic variants were used; mice homozygous for the autosomal recessive gene for diabetes (db/db), the phenotypically normal heterozygous (db/+), and the normal mice which lacked the diabetic gene (+/+). The mortality response of the +/+ mice to intraperitoneal inoculation with Coxsackie virus B4 differed from the response of the two genetic variants (db/db and db/+) derived from this strain. The db/+ variant was more susceptible to Coxsackie virus B4 than the parental background strain (+/+). The db/db variant was more susceptible than either of the other genotypes. Pathological findings of the pancreas of the three genotypes during the acute stage of infection closely paralleled the genotypically dependent susceptibility of the host.

No abstract

The ability of different strains of a single virus type to produce different pathogenic expressions is well documented within the picornavirus group. Coxsackievirus, group B, type 4 (CB4) has been associated with viral-induced diabetes in man, but expression of its potential to induce diabetes in experimental animals is variable. Evidence is presented here for one of the primary sources of this variability that could explain resulting contradictory reports offered in support or rejection of its diabetogenic potential. C57B1/6 and SWR mice were infected with the Edwards isolate of CB4 (CB4-Edw) and three of its plaque-purified virion "strains." These were designated Edwards isolate-1 (E1), E2, and E3. CB4-Edw, E1, E2, and E3 were serologically similar by infectivity neutralization tests, had identical plaque morphology, and replicated to a similar level in the pancreas. The most profound difference was the level of virus antigen accumulation in the islet cells as determined by immunoperoxidase localization. CB4-Edw had moderate antigen accumulation in most islet cells of SWR mice but was restricted to only a few specific cells within the periphery islets of C57B1/6 mice. Unlike CB4-Edw all three new isolates accumulated antigen in most islet cells of both mouse strains. Virus isolate (strain) E2 showed the most intense accumulation in islet cells. These observations suggest that the Edwards isolate of CB4, like other human isolates of CB4 virus, probably exists as a heterogeneous population of virion strains. The pathogenic consequences and expression of any diabetogenic potential is, therefore, dependent on virus strain selection. This diversity must be considered when evaluating the pathogenic nature of CB4 viruses in experimental animals and the possible role of the viruses in diabetes of man.

While surveying ichthyofaunal diversity in the tidal freshwater James River (near Richmond, Virginia) during March and September 1997, we observed that 40-50% of live fish collected had ulcerative lesions. Concomitant sampling upstream in nontidal reaches produced few fish with lesions (Յ2%). These observations were unprecedented based on similar surveys conducted annually since 1989 and subsequently through 2000. Affected taxa included cyprinids, catostomids, ictalurids, centrarchids, and moronids, representing both resident and migratory species. During this episode of tissue ulceration, free-living pathogenic amoebae, predominantly Acanthamoeba and Naegleria, were the primary organisms associated with lesions across all degrees of severity and across all host species. Based on the focal nature of the lesions, the lack of physical injury to surrounding tissues, the low numbers of fungi and pathogenic bacteria, the absence of Pfiesteria and related organisms, and the large numbers of free-living pathogenic amoebae isolated from all of the lesions, we suggest the epizootic event was an instance of ulcerative amebiasis. The 1997 event in the tidal James River was the first documented case of a fish epizootic from these amoebae in North America in over 20 years and is the first such event described for a mid-Atlantic coastal tributary.