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Overcoming anthrax – reviewing Russia’s anthrax control efforts

25 March 2020

A retrospective review of anthrax outbreaks in Tatarstan, a republic in the Russian Federation, indicates that widespread cattle vaccination can prevent zoonosis and keep the endemic infection at bay.

A recent paper published in the International Journal of Research in Pharmaceutical Sciences has reviewed the control and prevention strategies used to combat Tatarstan’s recurring cattle anthrax outbreaks from 1990 to 2019. The researchers found that strict vaccination protocols and early reporting kept case numbers low and prevented the spread of the disease to humans. Their analysis indicated that if the Republic of Tatarstan continues to vaccinate susceptible animals twice a year (in spring and autumn), anthrax rates will stabilise further, and the risk of zoonosis will remain low.

Background

During the first half of the 20th Century, Russia’s cattle herd experienced multiple anthrax outbreaks. Various regions in the Russian Federation struggle with anthrax, and the disease is endemic in the Republic of Tatarstan.

Though improvements in biosecurity and veterinary care have seen instances decrease in recent years, the risk of contracting anthrax in Tatarstan remains high. The region has multiple anthrax cattle burial grounds (including undocumented ones), and existing prevention strategies won’t eliminate the disease completely. Climate change is eroding Russia’s permafrost, exposing latent spores to the environment. There’s no harmless way to sanitise the foci of infections, and researchers can’t make any concrete recommendations on whether sterilising fields is an appropriate strategy.

In order to tackle anthrax, the Russian authorities carry out widespread vaccination campaigns for all susceptible livestock animals. The Soviet vaccination protocols required cattle and pigs to be vaccinated twice a year. Though this has been somewhat effective, there are drawbacks to this method. Vaccinations require manual handling and there are high risks of human error when they are administered. In addition, the risk of zoonosis is still high.

The study

Using archival documents from the Main Veterinary Directorate for the Republic of Tatarstan, researchers tracked reported anthrax incidences across three decades, beginning in 1990. They split the data into three cohorts: 1990 to 1999, 2000 to 2009 and 2010 to 2019. The researchers also identified multiple anthrax-disadvantaged permanently inhabited localities (ADPILs) and monitored disease activity.

Results

Since 1990, Tatarstan reported 26 anthrax outbreaks in farm animals. The outbreaks occurred in 16 of Tatarstan’s 43 districts, and researchers identified 26 ADPILs. Of these, 2.1 percent showed persistent anthrax activity. Over the course of the study, half of the ADPILs registered for the first time, indicating that there wasn’t complete eradication of the spores, or that the pathogen was being transmitted via wild animals.

The greatest instances of ADPILs and diseased animals occurred between 1990 and 1999. The researchers theorised that the spike in anthrax cases could be attributed to the collapse of the Soviet Union. During that period, the economy reorganised, and collective livestock farms were liquidated. The political and economic changes also put pressure on the state veterinary service.

During that period, 16 ADPILs showed disease activity. Of those, nine reported new instances, one had continual relapses and six were categorised as non-manifest (reported the disease in the past, but no recurrences during the study).

Between 2000 and 2009, active ADPILs and the number of sick animals decreased significantly. The total number of ADPILs fell from 16 to nine, and the disease was detected in eight cattle and one pig. The researchers found that four of the ADPILs were newly formed, four were non-manifest and one had a recurring case from 1999 to 2000.

The third period (from 2010 to 2019) had the smallest number of cases. Though there was an instance of cow to human transmission, the researchers attributed the zoonosis to human error. The sick animal was moved without being examined by a vet, and the handler became infected before state authorities could intervene.

During this period, the strategy for anthrax prevention changed. Tatarstan revived the Soviet-era vaccine protocols and began immunising susceptible livestock twice a year (in spring and autumn) to create herd immunity. In addition to vaccination, vets carried out antibody tests to identify unvaccinated or vaccine-tolerant animals and isolated them from the rest of the herd. The researchers found that this was an effective way to reduce instances of anthrax in cattle and pigs. It also led to a reduction in ADPILs.

Key conclusions

This analysis shows that animal vaccination and biosecurity can keep anthrax from infecting susceptible livestock and humans. Though anthrax remains endemic in the region, these steps will help Tatarstan stabilise its infection rate, despite the environmental challenges on the horizon.

Read the full review here.



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