Date: Mon 18 Jun 2018
Source: The New York Times [edited]
In this arid central African country [Chad], the long global struggle to eliminate a horrifying human parasite has encountered a serious setback: dogs. They are being infected with Guinea worms [dracunculiasis], and no one knows how.
Scientists are desperate to solve the puzzle. If the answer isn't found soon, or if the worms begin to spread widely into other species -- a handful already have been found in cats and even baboons -- then 32 years of work to end the scourge may crumble, said Mark L Eberhard, a parasitologist at the Centers for Disease Control and Prevention.
In 1986, when the Carter Center -- the global health philanthropy in Atlanta founded by President Jimmy Carter -- launched the eradication drive, an estimated 3.5 million people in 21 countries had worms.
Last year , only 30 human cases were found: half in Chad and half in Ethiopia.
But 6 years ago, here on the hot, dusty banks of the Chari River, the worms mysteriously began emerging from dogs. Last year , over 800 Chadian dogs had them.
Dogs cannot infect people directly, but they may carry the worms into ponds from which people drink, which is how humans are normally infected.
"They haven't caused a big human outbreak yet, knock wood, but that's my nightmare," said Ernesto Ruiz-Tiben, who directs the Carter Center's campaign.
To prevent that, Chad is paying villagers to tether dogs until all their worms wriggle out. The reward is $20 cash, plus a stout chain with 2 locks. (Dogs chew through ropes or are freed by children who take pity on them.)
The reward is $100 to humans with worms. To generate publicity, the cash is handed out at ceremonies held in the weekly roadside markets where villagers gather to barter meager fish hauls for goods like plastic buckets or quart bottles of gasoline.
At one such ceremony in Dangabol, in southeast Chad, Dr Hubert Zirimwabagabo, who heads the Carter Center's work in the country, played a quiz game with the audience, handing out bars of soap as prizes. Asked what caused worms, one winner shouted, to general laughter: "Drinking bad water -- and speaking ill of others."
Then Dr Zirimwabagabo asked local officials to present $100 to each of 3 women who had worms, reported them, and kept them away from drinking water. The officials obliged with grand ceremony, to loud ululations. People here may not see that much cash in a year. [Byline: Donald G McNeil Jr]
[HealthMap/ProMED-mail map of Chad:
The reservoir in dogs in Chad was discussed by the WHO in the 2014: "Dracunculiasis eradication: global surveillance summary, 2014" (Weekly Epid Rec. 2015; no. 19, (May 2015, pp. 201-15. <http://apps.who.int/iris/bitstream/handle/10665/242354/WER9019_201-215.PDF
>), which wrote "the unusually high number of dogs with confirmed Guinea-worm infections in Chad, which poses epidemiologic and biologic questions."
The contribution by the canine reservoir to maintaining infections in humans and whether they actually transmit the infection to humans by contaminating the water reservoirs is not known. A zoonotic reservoir is a potential complication to the attempts to eradicate dracunculiasis. - ProMED Mod.EP]
[In the majority of cases, under unhygienic conditions, both people and animals are affected by dracunculiasis.
Exceptionally, Guinea worm may occur as a purely animal infection. This was demonstrated during the last century, when 11 percent of stray dogs were found infected in Kizylorda (Kazakhstan), where no human infection was known.
In Uzbekistan and Turkmenistan, _Dracunculus medinensis_ has been identified in golden jackals (_Canis aureus_), which potentially can infect water sources.
_D. medinensis_ infection in dogs remains a challenge to global eradication, particularly in Chad and to a lesser extent in Ethiopia and Mali. - ProMED Mod.AS]