Horacio A. Delpietro

The common vampire bat (Desmodus rotundus) is a hematophagous species responsible for paralytic rabies and bite damage that affects livestock, humans and wildlife from Mexico to Argentina. Current measures to control vampires, based upon coumarin-derived poisons, are not used extensively due in part to the high cost of application, risks for bats that share roosts with vampires and residual environmental contamination. Observations that vampire bat bites may induce resistance in livestock against vampire bat salivary anticoagulants encourage research into novel vaccine-based alternatives particularly focused upon increasing livestock resistance to vampire salivary components. We evaluated the action of vampire bat saliva-Freund’s incomplete adjuvant administered to sheep with anticoagulant responses induced by repeated vampire bites in a control group and examined characteristics of vampire bat salivary secretion. We observed that injections induced a response against vampire bat salivary anticoagulants stronger than by repeated vampire bat bites. Based upon these preliminary findings, we hypothesize the utility of developing a control technique based on induction of an immunologically mediated resistance against vampire bat anticoagulants and rabies virus via dual delivery of appropriate host and pathogen antigens. Fundamental characteristics of host biology favor alternative strategies than simple culling by poisons for practical, economical, and ecologically relevant management of vampire populations within a One Health context.

Common vampire bats ( Desmodus rotundus ) are a key rabies vector in South America. Improved management of this species requires long-term, region-specific information. To investigate patterns of demography and dispersal, we analysed 13 642 captures of common vampire bats in Northern Argentina from the period 1969–2004. In contrast with findings from more tropical regions, we found reproductive seasonality with peak pregnancy in September and peak lactation in February. Curiously, sex ratios were consistently male-biased both in maternity roosts and at foraging sites. Males comprised 57% of 9509 adults caught at night, 57% of 1078 juveniles caught at night, 57% of 603 juveniles caught in roosts during the day, and 55% of 103 newborns and mature fetuses. Most observed roosts were in man-made structures. Movements of 1.5–54 km were most frequent in adult males, followed by young males, adult females and young females. At night, males visited maternity roosts, and non-pregnant, non-lactating females visited bachelor roosts. Males fed earlier in the night. Finally, we report new longevity records for free-ranging vampire bats: 16 and 17 years of age for a female and male, respectively. Our results are consistent with model predictions that sex-biased movements might play a key role in rabies transmission between vampire bat populations.

Ranchers have observed that residual hemorrhage decreases after livestock suffer repeated bites from common vampire bats (Desmodus rotundus). We hypo

During rabies outbreaks in cattle (paralytic rabies) in Argentina associated with the common vampire bat Desmodus rotundus, rabies was observed in marsh deer (Blastocerus dichotomus), red brocket deer (Mazama americana), capybara (Hydrochoerus hydrochaeris), savanna fox (Cerdocyon thous), and great fruit-eating bat (Artibeus lituratus). Rabies could constitute a threat to the survival of marsh deer in places where they live in small groups, and infection of both great fruit-eating bats and savanna fox represent a risk for humans; both species exhibit aggressiveness and fury when infected.

The authors describe the ecology of attacks by vampire bats and the epidemiology of rabies (paralytic rabies) transmitted by these bats in Argentina, based on data obtained from an epidemiological vigilance programme conducted between 1984 and 1993. It was found that rabies spread rapidly among vampire bats, causing high mortality (over 50%); subsequently, the population recovered slowly due to the low reproductive rate. This explains the features of paralytic rabies, such as high mortality among affected populations, brief duration and subsequent recurrence. Paralytic rabies occurs throughout the year without evidence of seasonal occurrence and with no relationship to rainfall. This is because vampire bats remain active within their habitat, neither hibernating nor migrating. The problem created by vampire bats depends on the ecosystem of their habitat. In the livestock ecosystem, the bats are synanthropic and their population is abundant. They feed almost exclusively on livestock and attacks on human beings are sporadic. In this ecosystem, paralytic rabies is a serious economic problem because of its frequency and readiness to spread (41 separate outbreaks were recorded in addition to an epidemic). On the contrary, in the scarcely populated livestock ecosystem, the vampire but population is much smaller; they feed on various species of animals, and attacks on human beings are more common, but paralytic rabies occurs only sporadically (one isolated outbreak). For overall control of paralytic rabies, the authors recommend reduction of the vampire bat population to a safe level, in order to break the chain of rabies transmission and diminish attacks by bats.