Over 120,000 refugees were living in four tented camps in the far northeast of South Sudan when I arrived in July 2013. Caught up in a complicated war in neighboring Sudan’s Blue Nile State, this diverse mix of people had fled the aerial bombings and ground attacks on their remote villages. Those who had warning herded together their handful of cattle, sheep, and goats and drove them along on their way to an uncertain future in the newly independent nation of South Sudan.
The population in this part of South Sudan swelled by a factor of five with the inflow of refugees. The sheep and goats ate up everything in sight, and in the dry season children could be seen in the tops of the few trees that hadn’t been cut for firewood, lopping off branches for their animals to browse.
The locals were not happy about the environmental degradation and tensions flared. Among other things, I was tasked with implementing a destocking campaign, in which excess sheep and goats were purchased, slaughtered, and the meat distributed to refugees and members of the local community. Sounds easy, but such projects often cause huge headaches and disruption in the community.
When destocking began, we found many of the butchered animals harbored one or more cysts (balloon-like structures filled with fluid) in the abdomen, anywhere from golf ball- to grapefruit-sized. These are the result of infection with parasitic tapeworms that can also infect people. As I read up on these parasites, I began to worry that the slaughter of so many animals in such a short time could inadvertently change the dynamics of the disease in the area.
The cysts may have been caused by the larvae of Echinococcus granulosus. This tapeworm is found around the world, but particularly in arid or semi-arid regions (including the southwestern US and southern Europe) where livestock play an important role. When these cysts are eaten by canines, from jackals and foxes to domestic dogs, the larvae mature into adults and latch onto the intestines, releasing eggs in the feces that contaminate the environment.
Many livestock – from sheep and goats to cattle, pigs and horses – ingest the eggs as they graze. Stomach enzymes prompt the eggs to hatch, while bile in the intestines stimulates burrowing through the intestinal wall into blood vessels, which carry them to various organs, most commonly the liver or lungs. Here they form cysts in which the larvae develop, ready to be consumed by a canine and continue the merry-go-round. It’s a very simple cycle as far as parasites go.
Tapeworms, like most other things, have not been studied much in this part of South Sudan. Research in Sudan, however, has shown the camel to act as the main livestock (or intermediate) host there. But camels do not fare well in the much wetter area of South Sudan where the refugee camps are located. Not more than a handful of camels were brought by refugees to the camps, and these seem to suffer much during the intense rainy season from April to October.
We set up a small survey that showed about 15% of the sheep and goats slaughtered in our project contained these cysts. With 1500 animals butchered in the destocking campaign, dozens of stray dogs had unprecedented access to the cysts as butchers tossed infected organs into the bushes for them to fight over. Quite a boon for the dogs and the tapeworms! But could it also affect the number of people with this tapeworm?
E. granulosus tapeworms are not well adapted to humans, probably because not enough people are eaten by dogs, foxes, or wolves to spread the parasite effectively. But some unlucky people, such as children playing on the ground in contaminated areas, occasionally become infected. Cysts begin growing usually in either the liver or lungs but occasionally in other organs, such as the heart, brain, or testicles.
Livestock rarely live long enough for the slow-growing cysts to become very big. But in some humans they can grow quite large over time, to over 8 inches (20 cm) in diameter. They press on organs and, in a small number of untreated cases, are fatal. If the victim receives a blow to the belly, a cyst may rupture, spreading fluid throughout the abdomen and seeding the growth of even more cysts from the released larvae. Severe anaphylactic (allergic) reactions can also occur when fluid escapes the cyst.
Treatment includes surgical removal or a technique in which a needle is used to aspirate the fluid from the cyst. This is followed by injection of high concentration saltwater or some other liquid toxic to the parasite larvae. If fluid leaks from the cyst during either procedure, new cysts can grow and may require more treatment later.
Fortunately E. granulosus infection seems to be generally rare in humans (with the mysterious exception of two relatively small areas in East Africa). Well under 1% of individuals appear to be affected, even among higher risk pastoralists in arid parts of the world. Diagnosis is difficult, but the parasite did not seem to be a major problem for people in this part of South Sudan. We did not witness any of the signs seen in the few heavily afflicted areas: older people with distended bellies from large abdominal cysts, as if they are in late pregnancy.
Control of the parasite includes reducing stray dog numbers, regular deworming of dogs, limiting access by dogs to cyst-infected organs of butchered animals, and good hygiene. Unfortunately none of these are easy to achieve in a refugee camp. Food was in short supply due to fighting elsewhere in South Sudan. Along with the environmental damage caused by the sheep and goats, the benefits of destocking seemed to outweigh the costs, including the potential to increase the incidence of tapeworm infections in animals and people.
In the end, we constructed three new slaughter slabs for the destocking campaign, and to be used by the communities thereafter. Each concrete slab was fenced in to prevent access by dogs and was fitted with a deep pit for disposal of cystic organs. Limiting access to dogs was about the only control measure we could influence much, though fences are notoriously difficult to maintain and are often allowed to deteriorate as their purpose is forgotten with time.
The destocking campaign was not ideal. Nothing ever is in a refugee situation. But hopefully it solved more problems than it created. Sometimes that’s the best you can hope for.
Eckert, J. and P. Deplazes (2004). Biological, Epidemiological, and Clinical Aspects of Echinococcosis, a Zoonosis of Increasing Concern. Clinical Microbiology Reviews, 17(1), 107-135.
Magambo, J., Njoroge, E., and Zeyhle, E. (2006). Epidemiology and control of echinococcosis in sub-Saharan Africa. Parasitology International, 55, S193-S195.
Romig, T, Omer, RA, Zeyhle E., et al. (2011). Echinococcosis in sub-Saharan Africa: Emerging complexity. Veterinary Parasitology, 181, 43– 47.