David L. Bergman

Molecular Inferences Suggest Multiple Host Shifts of Rabies Viruses from Bats to Mesocarnivores in Arizona during 2001–2009

In nature, rabies virus (RABV; genus Lyssavirus, family Rhabdoviridae) represents an assemblage of phylogenetic lineages, associated with specific mammalian host species. Although it is generally accepted that RABV evolved originally in bats and further shifted to carnivores, mechanisms of such host shifts are poorly understood, and examples are rarely present in surveillance data. Outbreaks in carnivores caused by a RABV variant, associated with big brown bats, occurred repeatedly during 2001–2009 in the Flagstaff area of Arizona. After each outbreak, extensive control campaigns were undertaken, with no reports of further rabies cases in carnivores for the next several years. However, questions remained whether all outbreaks were caused by a single introduction and further perpetuation of bat RABV in carnivore populations, or each outbreak was caused by an independent introduction of a bat virus. Another question of concern was related to adaptive changes in the RABV genome associated with host shifts. To address these questions, we sequenced and analyzed 66 complete and 20 nearly complete RABV genomes, including those from the Flagstaff area and other similar outbreaks in carnivores, caused by bat RABVs, and representatives of the major RABV lineages circulating in North America and worldwide. Phylogenetic analysis demonstrated that each Flagstaff outbreak was caused by an independent introduction of bat RABV into populations of carnivores. Positive selection analysis confirmed the absence of post-shift changes in RABV genes. In contrast, convergent evolution analysis demonstrated several amino acids in the N, P, G and L proteins, which might be significant for pre-adaptation of bat viruses to cause effective infection in carnivores. The substitution S/T242 in the viral glycoprotein is of particular merit, as a similar substitution was suggested for pathogenicity of Nishigahara RABV strain. Roles of the amino acid changes, detected in our study, require additional investigations, using reverse genetics and other approaches.

Predator and heterospecific stimuli alter behaviour in cattle.

Wild and domestic ungulates modify their behaviour in the presence of olfactory and visual cues of predators but investigations have not exposed a domestic species to a series of cues representing various predators and other ungulate herbivores. We used wolf (Canis lupus), mountain lion (Puma concolor), and mule deer (Odocoileus hemionus) stimuli (olfactory and visual), and a control (no stimuli) to experimentally test for differences in behaviour of cattle (Bos taurus) raised in Arizona. We measured (1) vigilance, (2) foraging rates, (3) giving up density (GUD) of high quality foods and (4) time spent in high quality forage locations in response to location of stimuli treatments. In general, we found a consistent pattern in that wolf and deer treatments caused disparate results in all 4 response variables. Wolf stimuli significantly increased cattle vigilance and decreased cattle foraging rates; conversely, deer stimuli significantly increased cattle foraging rate and increased cattle use of high quality forage areas containing stimuli. Mountain lion stimuli did not significantly impact any of the 4 response variables. Our findings suggest that domestic herbivores react to predatory stimuli, can differentiate between stimuli representing two predatory species, and suggest that cattle may reduce antipredatory behaviour when near heterospecifics.

Population Monitoring in Support of a Rabies Vaccination Program for Skunks in Arizona

Three population monitoring methods were evaluated in support of a trap/vaccinate/release program for controlling a bat variant of rabies virus in skunks (Mephitis mephitis) in Flagstaff, Arizona (USA). Skunks were the primary species targeted for population monitoring during the program, but feral cats were also monitored as they represented an abundant secondary vector species capable of rabies transmission. Skunks were vaccinated and released, except for a subset tested for rabies. All captured cats were placed in the local animal shelter. Spotlight surveys essentially did not detect skunks, and were not able to detect reductions in the cat population. Catch-per-unit-effort marginally tracked population trends, but a passive track index adapted for an urban setting was most sensitive for detecting changes in skunk and cat populations. Mark-recapture population estimates could not be validly calculated from the data on captures and recaptures due to multiple violations of analytical assumptions.

No adverse effects of simultaneous vaccination with the immunocontraceptive GonaCon and a commercial rabies vaccine on rabies virus neutralizing antibody production in dogs.

Parenteral vaccination campaigns are integral to the elimination of canine rabies. To maximize herd immunity in dogs, immunocontraception provided at the time of rabies vaccination should reduce fecundity and dog abundance. GonaCon has been used successfully as an immunocontraceptive in a variety of mammals, and by inference, the dog would be an ideal candidate for testing. As an initial step in evaluating a combination-vaccination program, we assessed the effects of GonaCon on rabies virus neutralizing antibody production in dogs after administration of a veterinary rabies vaccine. Eighteen feral/free ranging dogs were included in this initial study: six were given GonaCon only, six were given rabies vaccination only, and six received GonaCon and rabies vaccination. Antibody levels were evaluated over 82 days. The use of the immunocontraceptive GonaCon did not affect the ability of dogs to seroconvert in response to the rabies vaccine. Thus, GonaCon provides a potential immunocontraceptive for use in combination with rabies vaccine to increase herd immunity and address dog population over abundance to better manage rabies.

Vigilance in Cattle: The Influence of Predation, Social Interactions, and Environmental Factors

Abstract Vigilant behavior in wild ungulates is critical to guard against predation. However, few studies have examined vigilant behavior in domesticated ungulates. Considering the expansion of large predator populations, understanding vigilant behavior and factors that influence it will help with the management of livestock. We observed adult female cattle (Bos taurus L.) in open-range conditions where large predators (wolves [Canis lupus L.] and mountain lions [Puma concolor (L.).]) were common threats during summers of 2005 and 2006 in eastern Arizona. This study was designed to determine 1) to what extent cattle exhibit vigilant behavior compared to published data on wild ungulates, 2) whether predation events influence vigilance rates of cattle, and 3) whether social and environmental factors affect vigilance of cattle. Cattle exhibited vigilant behavior (3% ± 0.19%) during peak foraging periods, but at a lower rate than wild ungulates. Cows with calves were more than twice as vigilant (4.5% ± 0.46%) as those without calves (2.0% ± 0.27%). Single cattle and groups of two to five exhibited higher vigilance rates (4.2% ± 0.79%) than groups of six to 20 (2.5% ± 0.32%) and groups of > 20 (3.0% ± 0.41%). Cattle in groups of > 20 increased vigilance as visual obstruction increased. Mother cows whose calves were preyed upon (n = 5) exhibited a 3% to 48% increase in vigilance within 3 d after their calves were killed; this rate returned to near baseline levels after 10 d. Conversely, mother cows reduced foraging after their calves were killed from 88.5% ± 1.69% to 43.5% ± 11.4%; foraging rate also returned to near baseline levels after 10 d. Cattle exhibit vigilance at lower levels compared to wild ungulates, but this behavior appears to be at least partially an antipredatory behavior. Our findings provide support that predators can influence cattle behavior.

Response of ducks to glyphosate-induced habitat alterations in wetlands

The effects of glyphosate herbicide-induced changes in wetland emergent vegetation (largely cattails,Typha spp.) on densities of ducks (Anatinae) were assessed in northeastern North Dakota. In 1990 and 1991, 17 cattail-dominated wetlands were randomly assigned to 0% (reference wetlands), 50%, 70%, or 90% areal spray coverages with glyphosate herbicide. Densities of green-winged teal (Anas crecca), bluewinged teal (Anas discors), gadwalls (Anas strepera), and ruddy ducks (Oxyura jamaicensis) were similar among treatments during both post-treatment years (P≥0.1). One year post-treatment, mallard (Anas platyrhynchos) and northern pintail (Anas acuta) abundances did not differ among treatments (P≥0.1), whereas two years post-treatment their abundances were greater in the sprayed wetlands than in the reference wetlands (P≤0.1). Densities of northern shovelers (Anas clypeata) and redheads (Aythya americana) differed among treatments in both post-treatment years, with the 50% sprayed wetlands harboring more ducks than did the other three treatments. Percent coverage and hectares of open water were positively correlated with numbers of diving ducks (Aythyini and Oxyurini) (P≤0.1). Dabbling duck (Anatini and Cairinini) numbers correlated positively with hectares of open water and dead vegetation, whereas their numbers were negatively correlated with percent coverage of live vegetation (P≤0.1). Results of this study suggest that numbers of ducks were positively influenced by creating a mosaic of open water, live vegetation, and dead vegetation with glyphosate herbicide.

Effects of herbicide-induced habitat alterations on blackbird damage to sunflower

Abstract In August 1992, we treated cattail-dominated wetlands in four 23-km2 blocks with aerially-applied glyphosate herbicide (5.3 1 ha−1). Four other blocks of wetlands were left untreated (reference). We assessed the effects of cattail (Typha spp.) reduction on roosting blackbird (Icterinae) numbers and sunflower damage within the blocks. Blackbird numbers did not differ between posttreatment years (P = 0.453) or between treated and reference wetlands (P = 0.469), averaging 6227 ± 4185 (SE) birds per block. Sunflower damage within blocks was similar between posttreatment years (P = 0.250) and did not vary (P = 0.460) between treatments ( x = 2.9 ± 1.2% ). However, positive linear relationships were detected between blackbird numbers (y) and hectares of live cattails (x) [(y = 442.2 x)] (P = 0.006) and between blackbird numbers (x) and kilograms of sunflower lost per hectare per year (y) [(y = 0.003 x)] (P = 0.0001). Cattail reduction appears to discourage roosting blackbirds and, thus, may reduce sunflower damage in adjacent fields.

Visitation rate and behavior of urban mesocarnivores differs in the presence of two common anthropogenic food sources

Cat food left out for feral and domestic cats and bird seed spilled from backyard bird feeders are two common anthropogenic food sources that may attract non-target animals like urban mesocarnivores but no studies have quantified mesocarnivore visitation at these food sources. We used motion-activated video cameras to monitor mesocarnivore use of spilled bird seed below 25 bird feeders maintained by residents in four neighborhoods in Flagstaff, Arizona, June-September 2012 and 2014. During the first five nights of monitoring only seed that spilled naturally below feeders was available. On each of the subsequent five nights, we placed a bowl of commercially available dry cat food below feeders so that both spilled seed and cat food were present. In both years, after cat food was added, the number of visits by striped skunks (Mephitis mephitis), raccoons (Procyon lotor) and domestic cats (Felis cattus) doubled and the number of times two animals were present simultaneously also increased. Aggressive interactions, in the form of displays or contacts, increased for all species combinations but significantly only between skunks in the presence of cat food. These results demonstrate that both spilled bird seed and cat food may be exploited frequently by urban mesocarnivores and that the type of food can elicit different behavioral responses that could have important implications for human-wildlife conflict and disease transmission.

Potential risk to ring-necked pheasants from application of toxic bait for blackbird control in south Dakota

Blackbird (Icterinae) damage to sunflowers in the northern Great Plains can be locally severe. One approach to alleviating depredation pressure is to reduce blackbird populations through application of brown rice bait treated with the avicide DRC-1339. Because such baiting can potentially affect nontarget species, we conducted pen and field trials to evaluate the potential risk from avicide baiting to ring-necked pheasants (Phasianus colchicus). Although most female pheasants in pen tests preferred cracked corn and sorghum, 2 of 12 birds preferred brown rice. In 4-day trials within a 0.2-ha flight pen, pheasant consumption of brown rice from bait swaths simulating field bait applications was not affected by the presence of an alternate bait swath of cracked corn. Pen trials to evaluate possible avoidance responses following a sublethal dose of DRC-1339 showed that 2 of 7 birds shifted from their previously preferred feeding sites following exposure to the avicide. During March and April 1995, we recorded pheasant numbers in 6 pairs of 0.8-ha plots in corn stubble fields that were either baited with brown rice or were designated as reference plots. Overall, use of test plots was low, but at the most heavily used sites, pheasants visited reference plots more than baited plots (P = 0.004). We conclude that (1) pheasants will eat brown rice treated with DRC-1339; and (2) although chances of exposure to an acute lethal dose can be reduced by increasing the dilution, harmful repeated doses could be obtained because avoidance of feeding sites, following sublethal exposure, cannot be assumed.

Preference among 7 bait flavors delivered to domestic dogs in Arizona: Implications for oral rabies vaccination on the Navajo Nation

Abstract Less than 20% of the domestic dogs on tribal lands in the United States are vaccinated against rabies. One method to increase vaccination rates may be the distribution of oral rabies vaccines (ORVs). ONRAB® (Artemis Technologies, Inc., Ontario, Canada) is the primary ORV used in Canada to vaccinate striped skunks and raccoons. To investigate the potential use of ONRAB® ORV baits to vaccinate feral domestic dogs against rabies on tribal lands and beyond, we performed a flavor preference study. A total of 7 bait flavors (bacon, cheese, dog food, hazelnut, sugar-vanilla, peanut butter, and sardine) were offered in pairs to 13 domestic dogs. Each dog was offered all possible combinations of bait pairs over a period of 10 days, with each bait offered 6 times. The proportion of times each bait was consumed first by individual dogs was calculated and comparisons among dogs were conducted using the MIXED procedure in SAS (SAS Institute, Cary, NC). Pairwise comparisons between baits were performed using “contrast” statements with sugar-vanilla flavor as the default for comparison. Type 3 tests of fixed effects showed a significant treatment effect (F 6,72 =9.74, P <0.0001). Sugar-vanilla was selected first during 14% of the offerings and exhibited the least preference among all bait types (F 1,72 =22.46, P <0.0001). Dog food was selected first 56% of the time, and more frequently than all other bait types (F 1,72 =13.09, P =0.0005).