Re: INDONESIA - Bali: cats and dogs have BF
http://www2.defra.gov.uk/research/project_data/More.asp?I=SE0526&M=CFO&V=UEB
DEFRA Science and Research
Evaluating the potential of carnivore and scavenger species as sentinels of new and emerging diseases in the UK (SE0526)
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Description
Background
Pathogens tend to be generalists : i.e. they can infect more than one species of host, with some displaying very wide host ranges (e.g. Taylor et al., 2001; Cleaveland et al., 2001). This generalist nature is of particular concern for emerging diseases in human and animal populations, as these appear to be predominately associated with multiple hosts (Taylor et al., 2001; Cleaveland et al., 2001; Woolhouse et al., 2001; Woolhouse, 2002).
Outbreaks of infectious diseases originating from animal reservoirs are a continual threat to human public health (Daszak et al., 2000), with recent high-profile outbreaks of SARS, West Nile Virus (WNV) and Avian influenza highlighting the need for improved awareness, detection and co-ordination to combat new and emerging disease threats (RIVM, 2004; Kuiken et al., 2005; Butler, 2006).
The generalist nature of emerging multi-host pathogens poses challenges for understanding their epidemiology and implementing effective control. However, generalist pathogens also offer opportunities in terms of detection of infection, namely exploiting a range of hosts that might be useful as sentinel species. Although not yet widely used in veterinary and human disease detection, there is one group of hosts that have several characteristics that suggest they have the potential to act as useful sentinels: carnivore species.
Carnivores can be subdivided into true predators, (e.g. cats and foxes) which hunt and consume live vertebrate prey, and scavengers (e.g. corvids, such as rooks and crows), which opportunistically consume dead vertebrate species. Some species come into both categories, and most scavengers such as corvids will consume both prey and predator carcases.
The characteristics that make carnivores potentially useful sentinel species are as follows:
? First, carnivores are susceptible to a wide range of important human and animal infections. A high proportion (43%) of all zoonotic pathogens infect carnivores (Table 1), and thus carnivores represent a suitable taxonomic group for detecting many of the pathogens of concern to human health.
Table 1: Important animal host categories for zoonotic diseases (from Cleaveland et al., 2001)
Categories of host infected by pathogen Number of zoonotic diseases (n=800) Number of emerging zoonotic diseases (n=125)
All wildlife species 619 (77.4%) 113 (90.4%)
Birds 82 (10.3%) 23 (18.4%)
Carnivores 344 (43.0%) 64 (51.2%)
Rodents 180 (22.5%) 43 (34.4%)
Marine mammals 41 (5.1%) 6 (4.8%)
?
Second, infection of carnivores through oral ingestion of infected prey may be less pathogenic than infection of other hosts by other routes of transmission, such as inhalation or vector-borne transmission. High rates of seroconversion (with low morbidity or mortality) in carnivore and scavenger species have been recorded to a wide range of pathogens. Examples include rabbit haemorrhagic disease in foxes, where there is no evidence of pathogenicity, despite seroconversion (Philbey et al., 2005), and free-roaming (scavenging) domestic dog populations, in which seroconversion to Ebola virus (Allela et al., 2005), plague (Chomel et al., 1994: Leighton et al., 2001), Influenza A H5N1 (Butler, 2006) and anthrax (Cleaveland, unpublished data) have been recorded without evidence for widespread pathogenicity. We suggest that carnivores can be used to effectively ?sample? the environment for a wide range of pathogens present in different prey species.
? Third, a single predator or scavenger typically consumes material from more than one animal of a host species. This is likely to increase the probability of infection, essentially resulting in a ?bioconcentration? effect whereby a relatively rare infection in a prey species may be detected at a higher prevalence in the carnivore / scavenger species (a ?prevalence pyramid? ? Fig. 1).
Such ?bioconcentration? has been suggested as an explanation for the relatively high prevalence of antibodies in domestic dogs to Rift Valley Fever (House et al., 1996), Ebola virus (25%, Allela et al., 2005), African Horse Sickness (11%, Alexander et al., 1995), and anthrax (32%, Cleaveland, unpublished data) in endemic areas of Africa, the high prevalence of antibodies to rabbit haemorrhagic disease (RHD) in predators and scavengers in New Zealand (Parkes et al., 2004) and high seroprevalences to plague in domestic carnivores in Canada (Leighton et al., 2001). The Canadian study also showed that sampling domestic carnivores was both more sensitive and more efficient than previous surveys based on collection and culture of rodents and ectoparasites (Leighton et al., 2001) and domestic carnivore sampling has been suggested as a central component of plague surveillance in parts of the USA (Barnes et al., 1988).
An example of both the susceptibility to infection and exposure to multiple infections comes from a serological survey of rural dogs and cats in Canada which detected exposure to a range of emerging zoonotic pathogens, including Yersina pestis, Francisella tularensis, Rickettsia rickettsii and Sin Nombre Hantavirus (Leighton et al., 2001), suggesting that cats are suitable candidate sentinel species. A particular advantage of cats as sentinel hosts in the UK is that the age of cats is generally known, allowing generation of age-seroprevalence data that could provide valuable and precise information on patterns of infection, the timing of outbreaks and the introduction of infection into any given area.
In addition, corvids have been shown to become seropositive to many pathogens without developing disease, including Coxiella burnetii (To et al., 1998),and Borna disease (Berg et al., 2001), and may act as important natural reservoirs of some diseases.
The most common mammalian prey species in the UK consumed by indigenous wild and domestic carnivores are small rodents such as mice, voles and shrews, and rabbits. Garden birds are also a common prey item for domestic cats A recent study reported that 9 million British cats brought home 92 million prey items in a four month period, of which 57 million were mammals (largely mice, shrews and rabbits) and 27 million were birds (Woods et al., 2003).
These prey species are well known to have the ability to harbour many bacterial, viral and protozoal pathogens such as Leptospira species, (Twigg et al., 1969), Coxiella burnetii, (Webster et al., 1995), Borna disease virus (Rott & Becht, 1995), Hantavirus (McCaughey et al., 1996), and Encephalitozoon species (Wilson, 1979; Hersteinsson et al., 1993)
? In summary, carnivores are susceptible to a wide range of human and animal pathogens and can act as effective ?samplers? of vertebrate hosts, particularly birds and rodents, which are important reservoirs of many emerging diseases (RIVM, 2004). The high probability of exposure to pathogens through predation and scavenging is likely to enhance the cost-effectiveness of pathogen detection in carnivore species in comparison with other sentinel hosts.
*snip*
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Just as I suspected. Scavengers and carnivores don't get as sick when they eat dead birds as they would if they were kept in a closed room with them. What we are looking at appears to be B2Cat and B2Dog. Perhaps the take-home lesson is that eating raw dead chickens isn't as bad as sleeping with them... Ewwwwwwwwwwwwwwwwwwwwwww
