Trap-vaccinate-release and oral vaccination for rabies control in urban skunks, raccoons and foxes.

Two rabies control tactics, trap-vaccinate-release (T-V-R) and oral vaccination were used for the control of rabies in skunks (Mephitis mephitis), raccoons (Procyon lotor), and foxes (Vulpes vulpes) in metropolitan Toronto, Canada. Using T-V-R, a mean of 45% to 72% (95% confidence limits of 40% to 81%) of the skunks and a mean of 17% to 68% (95% confidence limits of 14% to 76%) of the raccoons in a 60 km2 area of Toronto were vaccinated against rabies between 1987 and 1991. The area has been free of skunk rabies from May 1989 to April 1992. Forty-five rabies cases were diagnosed during 1980 to 1986. In contrast, only three skunk cases have been reported since the vaccination program began in July 1987. The T-V-R area also remained rabies free during an epizootic of skunk rabies in metropolitan Toronto during 1991. Following distribution of rabies vaccine-baits throughout the ravines of metropolitan Toronto, June 1989 to December 1991, 46% to 80% of the Toronto fox population was immunized during 1989, 1990 and 1991. Only one case of fox rabies was reported in metropolitan Toronto since vaccination began, compared to 80 cases reported between 1982 and 1988. The area has been free of reported fox rabies from October 1990 to April 1992.     

Campaign against fox rabies in Belgium: 1st campaign for the vaccination of foxes by the oral route

The procedures followed in the first antirabies campaign carried out in Belgium with oral vaccination of foxes are described. Although the evaluation of the results is planned after the third campaign, preliminary data show a decrease in the expected number of cases in the vaccine treated zone.     

Echinococcus multlocularis infections of rural, residential and urban foxes (Vulpes vulpes) in the canton of Geneva, Switzerland

We examined 267 red foxes (Vulpes vulpes) from the canton of Geneva, Switzerland, for intestinal infections with Echinococcus multilocularis. This region is situated in the core area of the endemic range of this zoonotic cestode in Central Europe. Several factors were taken into account and urbanisation level appeared to be the most explicative to describe observed differences. The prevalence decreased significantly from rural and residential areas (prevalence of 52%, CI 43-62%, and 49%, CI 38-59 %, respectively) to the urban area (prevalence of 31%, CI 19-42%). A few juvenile foxes harboured very high burdens up to more than 120,000 worms and were significantly more heavily infected than adults. The intensity of infection decreased from rural and residential areas to the city, suggesting a lower contamination of the urban environment.     

Bait delivery for oral rabies vaccine to gray foxes

Rabies is a widespread zoonotic disease that has reached epizootic proportions in gray foxes (Urocyon cinereoargenteus) in central Texas. Because each species of carnivore has different food preferences and foraging strategies, it is essential that the efficacy of a bait delivery program be examined for gray foxes prior to an oral vaccination program being attempted. Field trials were conducted to determine bait preferences of free-ranging gray foxes to selected baits and odor attractants. Baits consisted of polymer cubes made of either dog food meal or fish meal, and a wax-lard cake that was enhanced with marshmallow flavoring. Attractants added to baits exuded sulfurous, fatty, cheesy, or sweet odors and flavors. During 3,589 operable bait station nights, gray fox visitation and bait uptake rates were 9.2% and 8.3%, respectively. Gray foxes exhibited no preference in bait uptake rates between bait and odor attractant combinations. Gray foxes exhibited no difference in cumulative bait uptake rates between onroad and offroad sites; however, the uptake rate by raccoons was significantly greater for baits placed on roads than for baits randomly placed. Raccoons were the major non-target species competing for baits, being attributed with 73% of the total uptake. Visitation and bait uptake rates by raccoons significantly increased after a 7-day lethal removal of raccoons (n = 37) from the study area. Random distribution of baits is recommended; it reduced bait uptake by non-target species without adversely affecting uptake by gray foxes.     

Oral vaccination of captive arctic foxes with lyophilized SAG2 rabies vaccine

Arctic foxes (Alopex lagopus) were immunized with lyophilized SAG2 oral rabies vaccine. The effectiveness of this vaccine was determined by serologic response and survival to challenge by rabies virus isolated from a red fox from Alaska (USA). No vaccine virus was found in saliva 1-72 hr after ingestion. At 2 wk after vaccination, all foxes had seroconverted, with rabies virus neutralizing antibody levels of 0.2-3.1 IU ml(-1). All vaccinated foxes survived to week 17 after challenge, and hippocampus, pons, and cerebellum were free of rabies virus as determined by direct immunofluorescence testing after death. One of four nonvaccinated foxes survived challenge and was free of rabies virus in neural tissue, and no rabies virus neutralizing antibody was detected in blood. Our results suggest that the lyophilized SAG2 oral rabies vaccine could be effective in arctic and subarctic regions, where freezing air and ground temperatures probably would not reduce its immunogenicity.     

Experience with antirabies vaccination of foxes using the oral route coordinated among several European countries and perspectives on the use of recombinant vaccinia-rabies virus

Campaigns of fox vaccination against rabies were carried out in Belgium, grand-duchy of Luxembourg and France in September 1986, June and September 1987. The SAD B19 attenuated strain of rabies virus, contained in baits (Tübingen baits) was used as vaccine. Baits were distributed at a range density of 11 to 15 baits per km2. First results are very encouraging. A recombinant vaccinia virus harbouring the rabies virus glycoprotein gene has been developed. This recombinant virus can be given to the fox by the oral route and protects it against rabies virus challenge; it is also innocuous for the fox and other non-target European species. A first trial of fox vaccination against rabies using this recombinant vaccinia-rabies virus has been carried out in Belgium, on a military domain, in October 1987.     

Immunization of arctic foxes (Alopex lagopus) with oral rabies vaccine

Arctic foxes (Alopex lagopus) were successfully immunized against rabies using an orally-administered, liquid SAD-BHK21 live virus vaccine in a sausage bait. Immunization was determined by serologic response and by resistance to challenge with an arctic rabies virus strain. Virus was not shed in saliva following oral vaccination, indicating that arctic foxes would not infect other foxes after ingesting this vaccine. High antibody levels were present in all experimental foxes 2 wk following initial vaccination. A booster vaccination at 56 wk induced a significant serologic response within 1 wk, suggesting an anamnestic response but titers began to decline within 8 wk in most foxes. Foxes were observed for 16 mo following the challenge and exhibited no symptoms of rabies. The SAD-BHK21 rabies vaccine in a sausage bait system has a strong potential for vaccinating wild populations of arctic fox.     

Feasibility of oral rabies vaccination campaigns of young foxes (<Emphasis Type="Italic">Vulpes vulpes</Emphasis>) against rabies in summer

Oral vaccination of foxes (Vulpes vulpes) against rabies has been shown to be highly effective. Several baiting strategies to increase vaccination coverage of the target population have been developed. For example, to increase the vaccination coverage of the young fox population before dispersal an additional summer vaccination campaign has been suggested. The effectiveness of such a campaign was evaluated using field data on home range size and shape of young foxes and a simulation model for aerial bait distribution. The results indicated that the limited ranging behaviour of the young fox population during the summer months severely reduced bait accessibility and consequently such an additional vaccination campaign would be very cost-ineffective.     

Lectins and microparticles for enhanced oral vaccination

Oral administration is an attractive means of vaccination since it alleviates the need for injection and trained personnel. Furthermore, effective oral vaccination induces immune responses locally in the gastrointestinal tract, the site of colonisation and infection by many pathogens. However, since most proteins and peptides are degraded in the gut, do not interact specifically with the epithelium, or induce strong immune responses, this route of delivery is generally inefficient. Two of the most promising potential approaches are the use of lectins to target vaccines to the epithelium and the association of vaccines with biodegradable microparticles. This paper describes methods to assess the stability of vaccines and targeting molecules in the gastrointestinal tract, interaction with the mucosa, uptake into internal organs and induction of mucosal antibody responses.     

A review of oral vaccination with transgenic vegetables

Mucosal immunization of the gastrointestinal tract is an effective way to stimulate local and systemic immune responses. Oral vaccines must be formulated in such a way that antigens are protected as they pass through the adverse environment of the stomach and are delivered to the mucosal inductive sites. Vaccine antigens cloned into edible transgenic plants are a promising new delivery system for oral vaccines. Such vaccines could be safe, inexpensive, and multicomponent.     

Borrelia burgdorferi in ticks of the Canton Tessin (Switzerland)

In the northern Alps it is hard to find an Ixodes ricinus population which does not harbour Borrelia burgdorferi. The infection rates range from 5 to 34% for adults and nymphs to 3.1% for larvae. This study shows that the infection rates on the southern side of the Alps are similar, at 25% for adults, 36.2% for nymphs and 3.2% for larvae. With respect to tick species other than I. ricinus, we did not succeed in finding any spirochetes in Dermacentor marginatus, Haemaphysalis punctata, Ixodes hexagonus, Rhipicephalus sanguineus.     

3 discoveries of amputations in Bern canton, Switzerland

At La Neuveville (Switzerland) close to the Blanche Eglise a separately buried amputated leg from the 19th century was discovered. The pathological lesions of the knee joints are most likely due to a nonspecific infection (Osteomyelitis). However, postmortal defects made an exact diagnosis difficult. Two foot-amputated male burials were discovered on St. Petersinsel (Switzerland) in the monastery cemetery of the 11th to 15th century. The possible causes of these amputations are being discussed within the historical context.     

New research on the oral vaccination of wild animals

Successful oral immunization of wildlife against rabies has strongly stimulated research in the past decade. New approaches have been developed for vaccine production (e.g.: use of recombinant vaccines) as well as for better potency or safety testing procedures. It appears that Man should also consider two important phenomena which already existed in nature before his research. The first one is an adaptation of the rabies virus, by serial passages, which favours the spreading of the disease among a sole animal species. Bites of this species vaccinate other species more often than they kill them, leading sometimes, to the mutual exclusion of potential vector. The next phenomenon is the self-control of the first one due to an over-adaptation of the virus to its vector species. It leads to unappropriate level, or delay, of reexcretion of the virus, therefore to the transformation of a rabies epizootics into rabies enzootics. Oral vaccination would thus appear as an useful tool to eradicate the disease after it reached this enzootic stage.     

Hepatozoonosis in foxes from Portugal

Hepatozoon, sp. is described for the first time in foxes (Vulpes vulpes silacea) in Portugal. Of 301 foxes examined, 143 (48%) were infected. The gametocyte was the predominant stage of the life cycle and was found in every organ except the bone marrow, where schizonts were the most abundant stage. The morphological similarity of this parasite's gametocytes to Hepatozoon canis is emphasized.     

Morphology of hair pigmentation in wild red foxes,silver foxes,and their hybrids

The effects of dominant allele Ar of locus Agouti on the morphology of hair pigmentation were described in foxes. The Ar allele was shown to determine the type of melanin and its content in hair with no effect on the morphology of pigment granules and their distribution throughout a hair. Using the method of electron spin resonance (ESR), the types of melanin (eumelanin and pheomelanin) and their content in the hair of red (ArArEE) and silver (aaEE) foxes and their hybrids (AraEE) were determined. In silver foxes, only one type of melanin (eumelanin) was found. In red foxes and their hybrids (which are phenotypically similar but darker than red foxes), both types of melanin (eu- and pheomelanin) were found. The highest melanin content was detected in the coat of silver foxes. In the hybrids, the total melanin content was lower than in silver foxes, but significantly higher than in red foxes. In red foxes, the contribution of pheomelanin to the total hair melanin content was twice as large as in the hybrids.