R. P. Hanson

FERAL SWINE IN THE SOUTHEASTERN UNITED STATES

In the southern part of the United States, the pig, Sus scrofa, is not only quite capable of getting along without the protection of man, but it probably has survived in this manner for four hundred years (Towne and Wentworth, 1950). The first swine to reach the United States were landed on the Gulf Coast in 1539 by Fernando De Soto (Lewis, 1907). Swine escaped from De Sotos entourage as he traveled over 3,000 miles through what is now southern United States. Other adventurers and the Spanish missionaries continued to introduce swine at intervals during the seventeenth and eighteenth centuries. Indians aided in the naturalization of the swine, as the animals that passed into their hands were usually allowed to roam free in the woods, a custom which many of their white brethren also followed. When the French attempted the settlement of Florida in 1560, Indians supplied them with pork from feral herds. In 1697, Jonathan Dickinson (1790), who put ashore for a day on what was probably St. Simon Island (Georgia), reported that Indians in his party went hunting for deer and hogs and brought in several of each. Such allusions to hunting swine are rather infrequent in early records. In spite of many reports that swine readily took to the woods in Carolina and Georgia and increased prolifically there, the animals must not have spread far from settlements. If they did, natives and travelers appear not to have considered them game. Moore (1840), who visited the coast of Georgia in 1744, and Kemble (1863), who spent the winter of 1838-39 on Butlers and St. Simon islands, do not mention feral swine in their accounts of game animals. However, there is no real evidence that feral swine ever disappeared from these areas. Salley (1911), who was secretary of the Historical Commission of South Carolina in 1911, asserts that feral swine were then to be found in the lower

The hemagglutination-elution pattern as a marker in characterizing Newcastle disease virus.

Test procedures were developed that make possible the use of HA-elution patterns from chicken erythrocytes for differentiation of NDV strains. The 53 strains and 16 clones examined were separated into 2 distinct groups of rapid and slow eluters. Both slow and rapid eluters were represented equally in the 3 NDV pathotypes (velogenic, mesogenic, and lentogenic). No relationship was found between HA-elution patterns and other properties of the same strain. It is feasible to use rate of elution as a genetic marker as well as a character for identifying NDV strains.

Susceptibility of Mink to Sheep Scrapie

A progressive, fatal spongiform polioencephalopathy was induced in mink intracerebrally inoculated with a suspension of brain from a Suffolk sheep with naturally acquired scrapie. The clinical signs and pathological lesions of the experimental disease were indistinguishable from transmissible mink encephalopathy, a disease of undetermined origin that occurs in mink.

Epizootiology of Newcastle Disease in Waterfowl

Antibodies to Newcastle disease virus (NDV) as measured by hemagglutination-inhibition and virus-neutralization tests were detected in 40/236 Canada geese captured while in their southward migration or in their wintering grounds. Antibodies were also found in 37/267 wild ducks and in 20/31 domestic geese. Adult geese were readily infected by several routes. Inapparent disease usually resulted, and only 1/13 cases were fatal. Goose embryos responded differently to inoculation with selected NDV strains than did chicken embryos of comparative developmental stages. Some goslings that hatched from inoculated embryos died and were found to have virus, whereas others survived and developed active antibodies. Four strains of virus isolated from migratory ducks of the Pacific flyway were characterized. All 4 strains were lentogenic but differed from lentogenic strains prevalent in chickens by being thermostable. It is proposed that wild waterfowl neither receive their ND infection from domestic poultry nor pass their disease to poultry. The virus reservoir probably exists in nature.

Cellular and humoral response of in ovo-bursectomized chickens to experimental challenge with velogenic Newcastle disease virus.

Humorally deficient, in ovo-bursectomized (Bx) and sham-Bx chickens were vaccinated twice, 1 month apart, with Newcastle disease virus (NDV) Roakin strain and challenged with a velogenic viscerotropic NDV strain via the oronasal route. Hemagglutination-inhibition and seroneutralization tests showed that Bx chickens had reduced antibody-mediated immunity to virus infection. In contrast, they had significantly higher cell-mediated immunity (CMI) before challenge, as estimated simultaneously by determination of blastogenic capacity of peripheral blood lymphocytes induced by phytohemagglutinin and by specific antigen stimulation. After virus challenge, there was transitory inhibition of CMI based on marked reductions in levels of stimulation indices, and this impairment in CMI was supported by persistence of virus in Bx chickens for longer periods. Bx chickens resisted challenge, even though antibody titers were well below those considered predictive of resistance to challenge, suggesting that CMI provides a degree of resistance to velogenic NDV.

Isolation of avian paramyxovirus-2 from domestic and wild birds in Costa Rica.

A survey for Newcastle disease virus (NDV) in wild birds of Costa Rica was conducted by swabbing wild-caught pet birds, backyard chickens, and wild birds captured in Japanese mist nets in tropical rain forests and agricultural areas. Cloacal swabs were collected from 876 birds of approximately 132 species representing 24 taxonomic families. Hemagglutinating agents were isolated from 18.7% of the birds. Paramyxovirus type 2(PMV-2) (Yucaipa-like), unreported in free-flying passerines in the Americas, was recovered from a finch, wren, and chicken, each from a different location. Pathogenicity trials with infected turkey poults and newly hatched chicks did not result in growth impairment or significant clinical signs of disease. Attempts to isolate NDV were negative.

Transmissible Mink Encephalopathy: Experimental Transmission to the Squirrel Monkey

A progressive, fatal spongiform encephalopathy developed in three squirrel monkeys 11 months after inoculation with primate-passaged transmissible mink encephalopathy agent. The clinical symptoms and histopathologic and electron microscopic findings suggest that this naturally occurring disease of mink has been transmitted experimentally to squirrel monkeys.

TRANSMISSIBLE MINK ENCEPHALOPATHY IN CARNIVORES: CLINICAL, LIGHT AND ELECTRON MICROSCOPIC STUDIES IN RACCONS, SKUNKS AND FERRETS*

Four raccoons and one of two skunks inoculated with brain suspensions containing the transmissible mink encephalopathy (TME) agent developed a neurologic disease characterized by alterations of behavior, by incoordination and by slowing of motor activity. Histologic examination of the brains revealed a spongiform polioencephalopathy as is characteristic of the disease in mink. Fourteen ferrets inoculated with TME brain suspensions remained asymptomatic until sacrifice 2 years post-inoculation. A spongiform degeneration of gray matter was present in all ferret brains. However, the lesions and their topographical distribution were distinctly different from those seen in the brains of all other species susceptible to TME infection.

Newcastle disease virus in waterfowl in Wisconsin

Newcastle disease virus was isolated from the cloaca of 1-5% of live-trapped waterfowl in Wisconsin in the fall from 1978-1980. Antibody to NDV was detected in 8% of the birds tested, with no apparent difference between sex and age classes. Experimental infection resulted in persistence of virus shedding for months after exposure. Lack of detectable antibody in some of the experimentally infected birds suggests that reported antibody prevalence may not be indicative of the true prevalence of the infection. Isolation of NDV for the last 9 years as well as the detection of antibody in waterfowl over 25 years ago, suggests a well-adapted host-parasite relationship. Experimental evidence of virus persistence in individual mallards (Anas platyrhynchos) provides a mechanism for maintenance of the virus in the wild population.

The viscerotropic pathotype of Newcastle disease virus.

SUMMARY The viscerotropic form of Newcastle disease is defined and the history of the present panzootic of this disease is reviewed. Evidence is presented to support the concept that the viscerotropic form is genetically different from established enzootic forms of Newcastle disease. Ways of differentiating the pathologic forms are described. Transmission of the virus is discussed so as to identify problems of controlling its spread and preventing further introductions.