CASE NOTES


RABIES—A TIMELY REMINDER

Alan Taylor, Central West LHPA

Posted Flock & Herd March 2012

INTRODUCTION

More than 55,000 people (mostly in Africa and Asia) die of rabies each year - that equates to one person every ten minutes. The World Organisation of Animal Health (OIE) held a Global Conference on Rabies Control in Korea last September, co-sponsored by Australia. Only 32 of the 178 OIE Member Countries are regarded as free of rabies, and at least 110 Member countries are considered endemically infected, and the annual cost of rabies is estimated at around $4 billion annually.

OIE CONFERENCE RECOMMENDATIONS ON RABIES CONTROL

Recommendations from the Conference included-

RABIES VECTORS

The OIE estimates that almost 99% of human rabies deaths are due to dog bites. A major problem is that in the early prodronal stage (lasting 2 to 3 days) the dog often realises there is something amiss, and seeks the support and company of the owner. As the rabies virus infects both nervous and non-nervous tissue at the same time the dog's saliva is infective during this 'comforting' stage (McGavin and Zachary 2007).

The Economist (2011), (as well as the BBC and AFP) reported on an outbreak of rabies in the Amazonian region of Ecuador in December 2011 - at that stage at least 12 people (including an eight month pregnant lady) had died due to bites from vampire bats. The local indigenous people trusted their local shamans rather than modern medicine, so the death total was expected to rise. A human vaccination program has begun, and interestingly some 170 bats were caught and doused with diphenadione, which will kill an estimated 2,000 to 3,000 of their mates as the treated vampires spread the poison through their colonies. Farmers' failure to report cases of rabies among their livestock contributed to the spread of the disease.

RABIES CONTROL IN THREE ENDEMIC COUNTRIES

Socio-economic conditions play an important part in rabies control and prevention. As examples we will look at three of these endemic rabies countries.

Canada

In western Canada rabies has been present in the arctic fox and skunks. When I worked in Saskatchewan one client lost 13 cows through bites from a rabid skunk. In those days brains were submitted to a laboratory in Alberta, and if the initial histology did not show Negri bodies, mice were inoculated and there was a 21 day wait before they could be examined for a conclusive Yes/No answer. The vaccine protocol then was the Fleury vaccine, a course of 14 very painful intra-abdominal injections. One colleague from Moose Jaw told me he stopped after the 7th treatment, and would rather risk dying of rabies. Thankfully modern vaccination protocol is much kinder (see WHO Guide for post-exposure prophylaxis of rabies).

There was an interesting paper presented at the 30th World Veterinary Congress (Oct. 2011) on the problem of rabies in racoons in the Province of Quebec. Historically racoons were moved from Florida to North Carolina to give the locals something to shoot at, and the imported animals brought rabies with them. The racoon rabies spread northwards, and by 2006 was diagnosed in racoons in Quebec. In response to this finding an enhanced surveillance program was put in place and rabies testing was done on sick or dead racoons, skunks and foxes reported by the public to a call centre or found alongside roads by patrol crews, as well as animals collected by professional trappers. Control measures included targeted depopulation and vaccination of the vector species. In discussing this later with Mr. Lair (the presenting author) he confirmed that the uptake of the oral vaccine was good in racoons, but skunks rarely ate the vaccine-inoculated bait. From 2006 to 2009 brain samples were tested by direct immunofluorescence microscopy, but 2010 testing has been performed locally with a direct immunohistochemical test developed by the CDC. Altogether over 11,400 animals have been tested; with 66 positives in 2007, 32 in 2008, and 2 in 2009.No cases were detected in 2010, suggesting the campaign has been very successful. The initial public response to the danger was excellent, the problem now being to keep the public aware and alert.

South Africa

Several papers were presented at the World Vet Congress on rabies in the different areas (see reference list) - the thought being that every rabid dog would infect one and a half susceptible dogs before dying, and that mass vaccination of dogs (at about $2 per dog) was far more cost efficient than post-rabies treatment of humans (around $10,000 per person). In Kwa-Zulu Natal province public vaccination of dogs was carried out - it being stressed that all dogs (including puppies) needed to be vaccinated, as the local young men often went away from their homeland to find work, and the family would give them a puppy for company to take with them.

Vaccination of domestic dogs not only protects the human population, but stops the spread of rabies into neighbouring wildlife areas and infecting the resident wildlife.

Indonesia

Dogs play an important role in Indonesian life. They are used as guards and hunters, as lucky companions for fishermen, and as a major source of animal protein particularly during religious festivities. So it is little wonder that both the locals and animal activists opposed a shooting/strychnine baiting attempt to eliminate dogs (and therefore rabies) on an Indonesian island. Many of the dogs were hidden or sent to another island (a good way to spread the infection).

Bali is an island dear to many Australian visitors, and rabies was diagnosed there in 2008, having been brought in by a fisherman's companion dog. To date there have been 119 human deaths since 2008, including 5 in 2011. A mass vaccination program for dogs was proposed, but due to a combination of inter-governmental politics and funding problems the scheme did not start until 2010. As it can take up to two years after being bitten for a human to die more deaths from rabies are predicted. A paper on 'Modelling Interventions for rabies elimination in Developing Countries' (Townsend et al, 2011) was interesting. The abstract states that they 'developed a stochastic, spatially explicit simulation to explore the effectiveness of different mass dog vaccination strategies'. In theory, if over 70% of the island dogs were vaccinated rabies would die out in three years, and if over 90% were vaccinated it would take only one year. It is wonderful to eliminate a disease by pressing buttons on a computer, and the Macquarie Dictionary defines stochastic as 'conjectural'. The reality on the ground is quite different, but this type of modelling is required to present to politicians in order to get the funds to actually do something.

My thanks to Dr. Helen Scott Orr (the Australian Team Leader in the Bali rabies project) for her personal comments on the actual situation in Bali. As well as the dog vaccination campaign which will hopefully start again in 2012, they have developed a simple straw technique for brain sampling for rabies (reducing the risk to the collector and allowing more time for sample transport). Many of the dogs in Bali were hard to catch for vaccination, and work is ongoing for an oral vaccine - the main problem (as opposed to the racoons in Canada) being that dogs will gulp down food, and a palatable bait which scratches the oral mucosa of the dog to help vaccine exposure is being investigated.

Maybe this presentation should have been titled 'Rabies - coming soon to an island near you'.

References

  1. Helen Scott-Orr: power-point presentation and pers. com.
  2. Peter Beers DAFF Canberra: pers. com.
  3. The Economist: The Americas Dec. 12th., 2011
  4. Pathological basis of Veterinary Disease 4th. Ed. 2007; McGavin and Zachary
  5. Townsend et al WVC 2011 abstracts p.74; Modelling Interventions for rabies elimination in Developing Countries
  6. Reininghaus B WVC 2011 abstracts p.74 Rabies control in wildlife in the SV Orphen Area
  7. Erin E. Rees, Denise B langer, Frederick Lelievre, Nathalie Cote, Louise Lambert (2011) abstracts p. 73; Enhanced surveillance of racoon rabies in the Province of Quebec, Canada
  8. Weyer J et al. WVC 2011 abstracts p.73; Human rabies in South Africa with special focus on recent outbreaks
  9. Rabies guide for post-exposure prophylaxis www.who.int
  10. Global Conference on Rabies Control - OIE Inchen-Seoul ( Republic of Korea) Sept. 2011

 


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