In the foothills of the Andes, in the Argentinian Patagonia, indigenous Mapuche communities live in a harsh environment with their sheep and goats. Their animals are a vital source of food and income in these remote areas – home to Argentina’s sheep farming - where resources are scarce.
“When we started in the late 1970s, the surgeons were the ones dealing with hydatid disease, and they did not comprehend what a veterinarian was doing working in public health” said Dr Edmundo Larrieu from the Zoonosis Department of the Río Negro Health Ministry. “The search of asymptomatic cases changed the profile of patients and field work, involving the mass treatment of dogs with arecoline, gained us the respect of the health workers and the community. The health team was consolidated, and it became a team that included surgeons, veterinarians, health workers, biochemists, nurses and rural teachers ... what we call One Health today.”
In the 1970s, cystic echinococcosis (CE) was identified as a serious public health problem in these communities, and a CE control programme in the Province of Río Negro was launched in 1980. The programme was developed and implemented by Dr Larrieu which is currently led by Dr Marcos Arezo.
In the first stage of the programme, health workers dewormed 11 500 dogs with praziquantel during their quarterly household visits, and the veterinarians were responsible for the surveillance systems. Both health workers and veterinarians worked together on education strategies targeting schoolchildren and rural households.
Early detection of CE was conducted in schoolchildren (aged 7–14 years) initially through serology, and, since 1997, with ultrasonography. Yearly ultrasonographic diagnosis is conducted by the local medical teams. Patients suspected or confirmed as having CE are treated as appropriate according to the status of their disease; often this involves treatment with albendazole.
“An increased tendency to work as a team, both interdisciplinary and inter-institutional, brings us closer to the concept of One Health” said Dr Marcos Arezo, Ministry of Health, Province of Rio Negro. “We are optimistic that this type of work and others such as vaccination of lambs will give good results. New strategies are being designed to identify families at risk in periurban areas and rural towns that still have strong links with the rural areas through regular visits and bring their dogs and customs such as home slaughter to the towns”.
After decades of disease control efforts, the incidence of infection decreased but new cases of infection in schoolchildren persisted. In 2009 the second stage of the programme began, involving the introduction of the EG95 vaccine in sheep, developed at the University of Melbourne (Australia).
“I am delighted to see the positive outcomes of the EG95 vaccine and the reduction of echinococcosis transmission” said Professor Marshall Lightowlers. “The farmers have accepted the vaccine as well as other aspects of the control programme – a reflection of the respect they have for the control programme.”
For the past 8 years the vaccine has been donated to the programme by Professor Marshall Lightowlers. Young lambs are given two doses of vaccine, followed by a booster at about one year of age. A total of 29 323 doses of EG95 vaccine have been administered since then. Dog deworming and education activities have continued to be implemented. The community is involved with the vaccination campaigns, and local schools and churches make their facilities available for the vaccination teams to use during field work.
Before the vaccine was introduced, necropsy of animals aged older than 6 years showed that 56.3% were infected with Echinococcus granulosus. Between 1999 and 2015, 34 new cases of CE (12 cases in children aged 1–10 years) were diagnosed in the area. Six years after the vaccine was introduced, a significant 62% reduction in the prevalence of ovine CE in old sheep (21.6%) has been observed, as well as a reduction in the number and size of hydatid cysts.
Consequently, the number of producers with infected animals decreased from 94.7% to 23.5%. In 2016, only 3 new cases of CE were diagnosed (1 case in children aged 1–10 years). The interim results of the vaccine’s impact have been published, and the programme is continuing.
There are many logistic challenges to working in the area. The control area is remote and may be inaccessible during winter and health workers can only reach some households by horseback.
There are no fences, and sheep may graze far away from the house; the vaccination campaigns are announced in the local radio so the farmers can enclose their animals before the vaccination team arrives, but that does not always happen. This makes it difficult to ensure regular deworming of the dogs, as well as reaching the desirable vaccination coverage.
Despite these challenges, the combination of dog treatment with the vaccine over a prolonged period of time is achieving its objective to reduce the incidence of CE in both livestock and humans.
Vaccination is proving to be a valuable tool, although difficult to implement in these remote environments, and is helping to further decrease the impact of CE in the communities beyond what was possible to achieve with dog deworming and education alone.