Field Studies Evaluating Bait Acceptance and Handling by Dogs in Navajo Nation, USA

Abstract

Mass parenteral vaccination remains the cornerstone of dog rabies control. Oral rabies vaccination (ORV) could increase vaccination coverage where free-roaming dogs represent a sizeable segment of the population at risk. ORV’s success is dependent on the acceptance of baits that release an efficacious vaccine into the oral cavity. A new egg-flavored bait was tested alongside boiled bovine intestine and a commercially available fishmeal bait using a hand-out model on the Navajo Nation, United States, during June 2016. A PVC capsule and biodegradable sachet were tested, and had no effect on bait acceptance. The intestine baits had the highest acceptance (91.9%; 95% confidence interval (CI), 83.9–96.7%), but the fishmeal (81.1%; 95% CI, 71.5–88.6%) and the egg-flavored baits (77.4%; 95% CI, 72.4–81.8%) were also well accepted, suggesting that local bait preference studies may be warranted to enhance ORV’s success in other areas where canine rabies is being managed. Based on a dyed water marker, the delivery of a placebo vaccine was best in the intestine baits (75.4%; 95% CI, 63.5–84.9%), followed by the egg-flavored (68.0%; 95% CI, 62.4–73.2%) and fishmeal (54.3%; 95% CI, 42.9–65.4%) baits. Acceptance was not influenced by the supervision or ownership, or sex, age, and body condition of the dogs. This study illustrates that a portion of a dog population may be orally vaccinated as a complement to parenteral vaccination to achieve the immune thresholds required to eliminate dog rabies.

Field Studies Evaluating Bait Acceptance and Handling by Free-Roaming Dogs in Thailand

“…The baits tested and study protocol applied in this study were identical to the ones in a study recently performed in the Navajo Nation, USA, and can therefore be compared directly, except for the small adaptation with the intestine bait. The overall bait consumption and estimated vaccination rate was lower in this study than in the Navajo Nation [ 15 ]. Most likely this is a direct result of the exceptional situation in Thailand where most street and temple dogs receive food from care-takers on a daily basis and malnourished dogs are extremely rare.…”

“…In Thailand, only six dogs (1.72%) swallowed the PVC-capsule. However, 42.86% of all dogs swallowed the same capsule during the field study in the Navajo Nation [ 15 ]. Swallowing the PVC-capsule should be avoided since it can cause problems like gastric intolerance in the dogs [ 23 ].…”

“…Swallowing the PVC-capsule should be avoided since it can cause problems like gastric intolerance in the dogs [ 23 ]. However, such adverse events were not reported with the same PVC-capsule during the study in the Navajo Nation and another field trial in Haiti [ 15 , 24 ]. Other factors, such as shape, texture, and size of the bait and capsule can also influence bait acceptance and bait handling, [ 15 , 16 ].…”

“…Three different baits were tested: intestine, fishmeal, and egg-flavored baits ( Table 1 and Figure 1 ). The two industrial manufactured baits, the fishmeal and egg-flavored baits, were identical to the baits used in a previous study [ 15 ]. The intestine bait was prepared manually and was slightly adapted due to problems encountered during its initial preparation.…”

“…If the dog discarded the vaccine blister or if the dog did not accept the bait, the bait was recollected by the observer. A multivariate analysis of a previous data set from the Navajo Nation, USA, based on a similar protocol resulted in an extremely poor fitted model predominantly due to the fact that most factors examined were qualitative instead of quantitative [ 15 ]. Hence, univariate data analysis using the statistical software package GraphPad Prism 6 was applied for this study.…”