Ask any political scientist: regime change has unforeseen consequences. The vacuum left in the wake of a collapsing leadership and the disorganization that follows, whether greeted with joy in the case of liberation or fear in the case of tyranny, brings unexpected change. For the central Asian states of the former Soviet Union in the early 1990s, among these aftereffects was the appearance of a curious and frightful little worm that saw, in the collapse of the monolithic political powerhouse, a bright opportunity for itself.
The administrative republics of the former Soviet Union in the year 1989, prior to the independence of Soviet republics following the fall of the Berlin Wall. Image: Perry-Castañeda Library (PCL) of the University of Texas at Austin. Click for source. Quickly after the Soviet Union’s dissolution in 1991, medical services were guttered amidst an atmosphere of severe economic hardship. The political and socioeconomic collapse precipitated, among a great many other changes, the cessation of canine infection control programs and veterinary public health services. Control programs for deworming dogs disbanded throughout the former Soviet-controlled republics, while the dog population concomitantly swelled (1). The state of veterinary health is too rarely considered as an integral component of human public health, but the two are intimately intertwined: what infects farm animals, domestic pets and flying fowl often affects us two-legged mammals as well, as outbreaks of SARS, swine flu, and West Nile Virus have repeatedly shown us. The parasitic tapeworm Echinococcus, which infects canine predators, also follows this trend and relies on the ancient relationship between humans and herding canines. It infects canids, such as foxes, wolves, and domestic dogs that feast on the carcasses of herbivores, typically sheep or cattle. These gentle intermediate hosts harbor the larval form of the worm, which they pick up while grazing and ingesting the parasite’s eggs that had been previously excreted in canid feces, a perfectly endless ouroboros, if you will, charting the tapeworm's life cycle.
The life cycle of the Echinococcus parasite. Image: Human echinococcosis, also known as hydatidosis or hydatid disease, is caused by the larval stages of the tapeworm. Image: CDC. Click for source. Canines clearly do the dirty work for this tapeworm, playing an indispensable role in its transmission not only to sheep and grazing animals, but also to humans. Humans become accidentally infected by consuming the eggs, often through vegetables and water contaminated by feces. The parasite goes on to seed and root itself in the lungs, livers, and, well, any visceral organ in the human body. Various forms of the disease may occur depending on the species. E. granulosus causes the cystic and less severe form of echinococcosis, with slowly enlarging cysts in the liver and lungs. E. multilocularis, more often associated with wild animals and hunters, is the nasty one that causes alveolar echinococcosis: cysts form throughout the body, aggressively metastasizing and bubbling away to form parasitic tumors in the body (2). It is more rare and far more fatal. This, as it so happens, is the species that is percolating its way through Central Asia at this very moment. Echinococcosis is a disease associated with high morbidity due to its colonization of vital organs; rupture of the cysts can result in overwhelming anaphylactic shock and death. Just as the tapeworm has a life cycle, so too does the epidemiology of echinococcosis transmission. Preventing transmission to humans begins with treating dogs and deworming programs are crucial to maintaining good public health, both for us gangly primates and for our oldest and most faithful companions. The collapse of these veterinary health programs in the former Soviet republics in the ‘90s sparked a slow burning trend of escalating canine infections with both the E. granulosus and E. multilocularis species.
A specimen of Echinococcus granulosus obtained from a dog. Dogs and other canids are the only definitive hosts for the Echinococcus genera; humans are accidental hosts and are infected by the larvae after accidental ingestion of eggs from food, water or fomites that have been contaminated with dog feces. Image: CDC/Dr. Peter M. Schantz The prevalence of infection in livestock and canines “parallels the increase in human disease incidence.”(3) Nearly 60% of the sheep in Uzbekistan harbor the parasite and reports of an increase in prevalence have been recorded in Kazakhstan, Kyrgyzstan, and Tajikistan (1). From humans to goats, pigs, and even camels, anything with legs and warm blood flowing through its veins appears to be a home for this tapeworm. In just one decade following the Soviet collapse, the incidence of cystic echinococcosis (CE) spiked four-fold throughout central Asia (1). In Kazakstan, cases of CE have surged from an annual 200 cases in the mid-1990s to a thousand cases every year; the most troubling aspect of this epidemic is the increase in the proportion of pediatric cases from around 20% to 32% (3). Similar epidemics have been recorded in Lithuania, Tajikistan, Turkmenistan and Uzbekistan (1). The increasing prevalence of echinococcus in Kyrgyzstan serves as a poignant example of how this parasite has embedded itself in the wake of the Soviet collapse. In this country nestled just against China, cases of the pulmonary form of E. multilocularis first appeared in 1996 and have been creeping upwards ever since. Over 65% of foxes carry the tapeworm infection with some animals carrying thousands of parasites (4). The dog population has soared and large numbers of canines reportedly scavenge for rodents freely and unconfined, further increasing the likelihood of transmitting the disease to humans and other animals. A recent review examining the echinococcosis outbreak in Central Asia noted that “with increased numbers of dogs and widespread rural poverty, E. multilocularis colonized dogs which were forced to hunt or forage for food."(1) Poverty can be a burden for our canine friends, too.
The gross pathology of a cyst caused by an unknown species of Echinococcus excised from a human lung. The liver is the most common organ involved, followed by the lungs. Image: CDC/Dr. Kagan Though the number of human infections in Kyrgyzstan seem low - the total number of cases from 1995 to 2011 hovered around 300 - a report published last summer by that government's epidemiology unit calls the situation an emerging epidemic. Considering the serious morbidity caused by the disease, any number of infections is cause for concern. The echinococcosis situation in Kyrgyzstan and its neighboring countries is intrinsically tied to the disintegration of the Soviet Union and the ensuing “severe economic hardship” and socioeconomic changes (4). The collapse of the Soviet Union precipitated staggering changes in its previously centralized health services system: a collapse in funding, decentralization and fragmentation, the introduction of market relationships, and rising socioeconomic inequalities (5). Several new negative health trends ensued: decreased life expectancy and birth rate, increased incidence of infectious diseases, cardiovascular disease, as well as maternal and infant mortality (5). Amidst the deteriorating human public health system, programs for the good health of domesticated animals also fell by the wayside. As has been previously emphasized on this blog, when public health works, its effects are camouflaged and unseen. The emergence of disease or disaster materialize upon its absence or failing. Echinococcosis disease is an ugly indicator of the lingering fallout from the dissolution of the Soviet Union. The falling dominoes began with one of the biggest political and socioeconomic shake-ups in modern history, the effects of which continue to reverberate today, echoing as a slow public health disaster, manifesting as tapeworms nesting in the organs of livestock, dogs, and humans. N.B. Adjustments in husbandry techniques have also shaped the emergence of this post-Soviet epidemic. The spread of echinococcosis has indubitably been influenced by “the reorganization of livestock farming with the privatization of large collectivized livestock units [which] has also led to the closure of large meat processing units and reduced supervision of meat processing by the veterinary public health services." (1) With the shift to privatized farming, the need for farm dogs to shepherd increased, a situation ripe for the parasite to embed itself within a new social landscape. Resources Echinococcosis has previously been covered on this blog before: "Man's Best Friend, the Turkana Tribe & a Gruesome Parasite." A great article (and free, too!) looking at the epidemiological transition in the former Soviet Union, examining "Russia's health crisis, financing, and organization and public health reform need." What does bad public health look like? Previously on Body Horrors: A Mess in Texas: What Happened in Dallas with West Nile Virus?References 1) Torgerson PR. (2013) The emergence of echinococcosis in central Asia. Parasitology. 140(13):1 667-73 2) Centers for Disease Control & Prevention. (CDC) (December 12, 2012) "Parasites - Echinococcosis." Accessed April 28, 2014 at http://www.cdc.gov/parasites/echinococcosis/ 3) Torgerson PR et al. (2006) Present situation of cystic echinococcosis in Central Asia. Parasitol Int. 55 Suppl: S207-12 4) Usubalieva J et al (2013) Human alveolar echinococcosis in Kyrgyzstan. Emerg Infect Dis. 19(7): 1095-7 5) Danilovich N. (2010) Growing Inequalities and Reproductive Health in Transitional Countries: Kazakhstan and Belarus.J of Public Health Policy. 31(1): 30-50
