New Indian data cuts worldwide human rabies death toll by 40%
From ANIMAL PEOPLE, June 2012:
New Indian data cuts worldwide human rabies death toll by 40%
DELHI, CHENNAI, VISAKHAPATNAM–New Indian data on April 29, 2012 cut the estimated worldwide human death toll from rabies by more than 40%, with global repercussions for street dog population control, public health, and disease eradication funding priorities that are just beginning to be felt as rabies control experts become aware of the finding.
Presenting the most recent Indian government statistics on mortality from all causes to the Lok Sabha, the Indian parliament, Indian health minister Gulam Nabi Azad mentioned almost in passing, after discussing heart disease, diabetes, and cancer, that only 223 human rabies deaths were recorded in India in 2011, barely 1% of the 2002 government estimate, and just a seventh of the Indian toll from snakebites.
Snakebites killed 1,440 Indians in 2011, more than were killed by tigers, lions, leopards, elephants, bears, wolves, and all other wild mammals combined. India has long been thought to lead the world in human deaths from canine rabies, but now appears to have far fewer human rabies deaths than Pakistan, believed to have about 5,000 human deaths from rabies per year; China, with about 2,400; Indonesia, whose toll is variously reported at 900 to 5,000; Bangladesh, acknowledging about 2,000; and Nigeria, with about 1,000.
The drastic reduction in estimated human rabies deaths in India suggests that rabies is much less a public health scourge than is widely believed, and is accordingly much more vulnerable to eradication with a concerted push to vaccinate street dogs.
Worldwide, rabies was believed to be killing about 55,000 people per year, with canine rabies most prevalent in Southeast Asia and Africa, while bat rabies predominates in South America. The new Indian data suggests that the actual human rabies toll is less than 35,000, and that infection from dogs could be reduced to the point that globally, bats might soon be the primary vector for human cases.
Snakebite vs. rabies
Forwarding information obtained by ANIMAL PEOPLE from a variety of Indian sources, the International Society for Infectious Diseases broke the news of the reduction in estimated Indian rabies deaths on May 1, 2012 via the Program for Monitoring Emerging Diseases. Founded in 1994, the peer-reviewed ProMED-mail network now reaches more than 40,000 public health professionals in 185 nations.
ProMED-mail viral diseases moderator Craig Pringle, a Univeristy of Warwick professor emeritus, pointed out that while the Indian snakebite death toll may be difficult to reduce, human deaths from rabies could be eliminated entirely through more effective use of existing vaccines.
“Venomous snakes occur throughout many regions of the world and are a threat to public health, especially in the rural tropics where they are most abundant,” Pringle posted. “Out of more than 3,000 species of snakes in the world, some 600 are venomous and over 200 are considered to be medically important. The risk of snakebite is a public health hazard that many people in the rural tropics face on a daily basis.
“Snake antivenom immunoglobulins–antivenoms–are the only specific treatment for envenoming by snakebites,” Pringle continued. “Antivenoms can prevent or reverse most snakebite effects,” but “The production of antivenins is hazardous and requires the use of living animals.”
Because of “The complexity of the production of antivenins, the decreasing number of producers, and the fragility of the production systems in developing countries,” Pringle noted, “the high mortality from snake bite in India is understandable and excusable. The high mortality from rabies virus infection is less so. Potent and effective cell-produced anti-rabies vaccine and immunoglobulin are available and completely protective if administered soon after exposure. Further, the vectors of rabies virus are predominantly urban and feral dogs,” who can be vaccinated and sterilized to prevent the existence of a population vulnerable to canine rabies.
“The World Health Organization has claimed that there were about 20,000 human rabies deaths per year in India between 1992 and 2002,” e-mailed longtime Blue Cross of India chief executive and Animal Welfare Board of India member Chinny Krishna to ANIMAL PEOPLE, “but the figure given by Gulam Nabi Azad is in the opinion of many of us working on the ground much closer to reality.” Krishna’s e-mail was included as a letter-to-the-editor in the May 2012 edition of ANIMAL PEOPLE, inserted into the layout just before the press deadline.
Introducing the use of street dog vaccination and sterilization to combat canine rabies in 1966, Krishna became skeptical of the WHO and Indian government estimates of human rabies fatalities by 1976. At that time the official human rabies death toll in India was 35,000 per year.
“For at least 25 years, I fought the claim of 35,000 rabies deaths in India yearly,” Krishna recalled in an e-mail to members of the Federation of Indian Animal Protection Organizations. “I spoke at the Association for Prevention and Control of Rabies in India conference at Bhubaneshwar when the decennial figures for 1992-2002 were released,” lowering the estimated toll to 17,000 diagnosed human deaths and 3,000 deaths that went undiagnosed. “I was a lone voice disputing the updated figures of 20,000-odd rabies deaths per year during this period,” Krishna wrote.
Krishna suspected that the high figures were produced by the combination of inadequate case tracking, faulty diagnostic work, and official projections based on obsolescent and inaccurate presumptions about how rabies spreads.
Eventually Krishna persuaded People for Animals founder Maneka Gandhi, who for more than five years was the Indian federal minister for animal welfare, and was also for a time minister for statistics, but Mrs. Gandhi lost her cabinet position before she could organize an official reappraisal of the rabies numbers. Likewise convinced was Animal Welfare Board of India chair Rammehar Kharb, a retired military veterinarian who on appointment in May 2006 pledged to “eradicate rabies from India by mass vaccination of stray dogs.”
WHO-South East Asia Regional Organization technical officer for veterinary public health Gyanendra Gongal also came to question the official numbers.
Journalist Hiranmay Karlekar in a 2008 book entitled Savage Humans & Stray Dogs attributed the inflated human rabies death estimates to the desire of makers of post-exposure vaccines to sell more of their product to dog bite victims and to their biggest customers, the government clinics that are mandated to treat dog bite victims free of charge.
ANIMAL PEOPLE pointed out repeatedly, beginning in 1997, that several mosquito and tick-borne diseases, common to India but only recently medically identified, also produce high fever and other rabies symptoms, and are likewise frequently fatal if left untreated. Undetected insect-carried febrile illnesses could easily have accounted for most of the unconfirmed “rabies” death toll.
But before Indian health minister Gulam Nabi Azad’s April 29, 2012 statement to the Lok Sabha, there was little sign that the Indian health bureaucracy was taking notice.
Krishna sought unsuccessfully on several occasions to enlist FIAPO members to participate in an unfunded national rabies data collection effort. At the June 2011 Asia for Animals conference in Chengdu, China, Krishna assembled representatives of the AWBI, ABC India, ANIMAL PEOPLE, and Humane Society International for an informal brainstorming session which concluded that available information on clinically confirmed rabies cases suggested that the annual human rabies death toll in India could not be more than 2,000 to 3,000.
Data from Andhra Pradesh and Goa states, released after rabies outbreaks in 2011, later projected a range of 2,000 to 3,150 human rabies deaths per year, if all states were afflicted to the same extent.
“I would not necessarily go so far as to say that the number of human rabies cases a year in India is around 2,000,” Humane Society International president Andrew Rowan said at the time, “but I certainly suspect it is well below 20,000.”
What fewer deaths mean
The reduction in the official Indian government estimate of human rabies deaths from 20,000 to 223 “shows the massive contribution made by nonprofit organizations and the Animal Welfare Board of India,” particularly through the Indian national Animal Birth Control program, Krishna e-mailed to ANIMAL PEOPLE and FIAPO.
Countered Visakha SPCA and ABC India founder Pradeep Kumar Nath, “Until and unless we have more than 70% coverage of the entire country under the [federally funded] Animal Birth Control program, we cannot prove claims that the drop in human rabies deaths was due to our work. Effective ABC is not happening in 90% of India,” Nath charged.
Depending on how the new Indian rabies death toll is interpreted, it might either be seen as demonstrating the efficacy of ABC and the need for expanded ABC programs, or as showing that ABC has not been a factor in the improvement and need no longer be funded.
While Krishna was first to demonstrate the efficacy of the ABC concept, eradicating rabies from Chennai and surrounding parts of Tamil Nadu state, Nath in Visakhapatnam achieved the most rapid sterilization and vaccination of 70% of a municipal dog population on record in India, eliminating rabies from Visakhapatnam and the surrounding suburbs called the Visakhapatnam Circle.
Rabies returned to both the Chennai suburbs and the Visakhapatnam Circle in 2010, however. In the Chennai area, public officials failed to report isolated cases promptly, so that the Blue Cross of India could intensively vaccinate dogs to prevent the outbreaks from spreading. In Visakhapatnam, the Visakha SPCA lost the municipal ABC contract after a change of government. The new service provider failed to promptly start a high-volume vaccination and sterilization program to replace the Visakha SPCA services.
Nath spent much of 2011 leading vaccination drives against rabies outbreaks elsewhere in Andhra Pradesh, with material support from Krishna.
At issue between Nath and Krishna was not any substantive disagreement about the efficacy of mass dog vaccination and sterilization, but rather to what extent the drop in the government estimate of human rabies deaths reflects program success, as opposed to better record-keeping and data analysis.
Indeed, India as a whole is nowhere near achieving the 70% vaccination level that would be needed to eradicate rabies, nor the 70% dog sterilization rate that would be necessary to prevent increases in the population of unvaccinated street dogs. However, the examples of Chennai, Visakhapat-nam, Jaipur, Kalimpong, and other Indian cities where 70% vaccination and sterilization rates have been achieved show that rabies outbreaks can be kept from spreading, even where they occur, if they encounter barrier populations of immunized dogs. This does not prevent rabies from jumping beyond a vaccinated barrier population, if infected animals are transported. But, since rabid animals seldom wander far beyond their accustomed habitat, such jumps are relatively rare–especially for dogs, who are much less likely than bats or even raccoons to stow away in cargoes being hauled from city to city.
As Nath argued, to eradicate rabies throughout the whole of India would require achieving 70% vaccination and sterilization rates throughout India. But to isolate and eradicate individual rabies outbreaks, it is only necessary to achieve 70% vaccination in the areas surrounding those outbreaks.
Continued Nath, “In Kakinada, dogs were killed by the hundreds by political mafias, and there was no ABC program in place at all. Shall we attribute the decline in rabies in Kakinada to these killings? What are we to say here?”
Such examples chiefly illustrate a continuing need for better public education about rabies–and, indeed, about the transmission of infectious disease in general.
Attempting to kill the vector is the oldest and most widely practiced response to rabies and other infectious disease. Killing an actual or suspected vector species often appears to be successful in controlling the spread of a disease for short periods of time, but the appearance of success is illusory.
What actually happens is that when any very virulent disease kills so many of the host animals that it can no longer spread rapidly from host to host, it either burns itself out or evolves into a less virulent form, which can be incubated and spread for much longer before the onset of the fatal symptoms.
When all dogs exhibiting active symptoms of canine rabies are killed, along with any other dogs who can be caught, the remaining dogs tend to be the most furtive and nocturnal part of the population–the so-called pariah dogs of India, Pakistan, and Bangladesh, for example, who unlike street dogs who beg for handouts, live entirely by scavenging, avoiding human contact.
Rabies may persist among these dogs for many months in the latent “dumb” phase. When pariah dogs die, the deaths go unobserved. Eventually, months or years later, rabies returns from the pariah dog population to infect street dogs, community dogs, and pet dogs. Often this is perceived as a new infection-but it is really just the same old outbreak, cycling back into the community from a seldom-seen and sometimes almost invisible reservoir.
When the street dogs, community dogs, and pet dogs are vaccinated, rabies is no longer able to re-enter the community from the pariah dog population. After infected pariah dogs die, without having passed rabies to any others, the rabies outbreak dies too.
Canine rabies in China
A similar dynamic is involved in the persistence of canine rabies in southern and central China, but with the difference that in China the most frequent intermediary vectors between rabid feral dogs and humans appear to be not street dogs, nor unvaccinated pets, but rather some of the estimated 10 million dogs per year who are raised, transported, and sold for human consumption.
The Chinese ministry of health in September 2009 produced the estimate that rabies had killed about 2,400 people per year in China during the preceding five years.
“Most rabies deaths occurred in the Guangxi Zhuang Autonomous Region and the provinces of Guizhou, Guangdong, Hunan, and Sichuan, accounting for 61% percent of the total, China Daily summarized.
Contiguous to each other, the Guangxi Zhuang Autonomous Region and three of the four named provinces together form the part of China which is most involved in the dog meat industry. Southern Sichuan borders on Guizhou and is also involved in exporting dogs for slaughter.
China Daily noted that rabies infections “mostly occurred in rural areas among males,” who might be most likely to work among unvaccinated “meat dogs,” children under the age of 15, who are most likely to play with dogs, and “people over the age of 50,” the age bracket most likely to consume dog meat.
Dogs raised for meat in China are not vaccinated against rabies because the Chinese Veterinary Medicine Administrative Regulations state that vaccinating animals intended for human consumption against rabies is illegal. Transporting dogs who have not been vaccinated against rabies from one province to another is also illegal.
Thus leading Chinese animal advocacy attorneys Lu Xun, An Xiang, and Cai Chunhang contended at a June 2011 press conference in Beijing that most of the Chinese dog meat trade is illegal, even in absence of any law specifically prohibiting it. –Merritt Clifton
A formal review of the methodology of successful rabies eradication, worldwide, is accessible in “How to eradicate canine rabies: a perspective of historical efforts,” by Merritt Clifton, Asian Biomedicine Vol. 5, No. 4, August 2011; pp. 559-568, downloadable from <http://abm.digitaljournals.org/index.php/abm/article/viewFile/742/480>.