The worm H. contortus is the main goat and sheep health problem worldwide. The vaccine, which was developed by Scottish researchers, reduces H. contortus worm infection in animals. Tests showed an efficacy level between 80% and 90% in sheep and between 60% and 70% in goats. Vaccination is a clean measure, which leaves no trace in meat or milk and does not require a preharvest interval. Adequate nutrition contributes to reducing parasitic infections in animals, especially with regard to H. contortus. A vaccine that can help goat and sheep farmers control verminosis, the main health problem of those herds in Brazil, was validated by Embrapa in animals from Northeastern Brazil and showed an efficacy level between 80% and 90% in sheep, and between 60% and 70% in goats. The vaccine, developed by researchers at the Moredun Research Institute (Scotland, UK), is a preventative measure and does not stop infections, but rather increases the animal's response against the hematophagous (i.e. blood-feeding) worm H. contortus. Marcel Teixeira, a veterinarian and researcher at Embrapa Goats and Sheep (Sobral, CE) who was responsible for the vaccine validation study, says that it is not capable of eradicating the parasite. "In fact, we tried to reduce the parasite load and the impact of the disease to a point where the animals can produce without significant losses or mortality," he explains. The researcher says that H. contortus is a serious problem, the parasite feeds exclusively on blood and causes anemia and high mortality, thus economically impacting production systems. The most common way to control the problem is with vermifuges (dewormers). But as they are continuously and often incorrectly used, resistant worms are selected with each treatment, increasingly reducing the efficacy of the drugs available. "With the vaccine we do not have this problem, because the worm does not develop resistance against it," he explains. Another advantage is that vaccination is a clean measure: it does not leave any traces in the meat or milk, so it does not require a preharvest interval, that is, farmers do not need to wait a while to slaughter the animal or discard the milk after the vaccine. Photo by: Igor Magalhães Vaccine efficacy and costs The validation of the vaccine against the H. contortus was initially performed on an experimental scale in the herds at Embrapa Goats and Sheep, in Sobral, Ceará. Then the team expanded the experiment to herds in other properties in the Brazilian Northeast, especially in the state of Bahia. The findings indicated that the animals' response to the vaccine varies across species and, in the same species, it changes according to each breed. Sheep respond better than goats. And for some sheep breeds, such as Santa Inês, the effectiveness of the vaccine is higher. The protocol used in the Brazilian semiarid region was three pre-immunization doses, with an interval of 21 days, and a booster dose after six weeks in naturally infected animals. The vaccine requires some conditions to work well. It needs to be very well applied, stored in refrigeration, and it requires booster doses. The cost of the drug today, without import tariffs, is US$0.50 per dose, which is equivalent to the price of a high-cost vermifuge in Brazil. "The main disadvantage in comparison with other methods would be the cost, which ends up being higher, but it is compensated given that discarding milk and meat production is not needed as is the case with deworming drugs," Teixeira observes. Rony Gleidson dos Santosis a meat sheep farmer in the town of Pintadas, BA, and participated in the vaccine validation experiment in the field. He explains that he used to treat his herd with dewormers. "With this vaccine that Embrapa used here it was much better, the incidence of worms decreased a lot. I am interested in using the vaccine as soon as it is available," he reports. Teixeira notes that the practice normally adopted by breeders is incorrect, as they resort to different dewormers and it leads to parasite resistance to all the drugs in use. The advantages of the vaccine have already been proven; the next step is to carry out longer and more extensive studies in different regions, for the purposes of registration with the Ministry of Agriculture and Livestock (Mapa), the body that authorizes its trade, in order to start the process of imports and sales. "There is an initial administrative process and an interest from the manufacturer, from Embrapa and from the production chain. There is already a movement to bring this vaccine to Brazil and Embrapa is helping in this process," the researcher states. Suitable diet benefits animals with worms Suitable nutrition contributes to improving herd resilience to parasitic infections, especially with regard to Haemonchus contortus. The veterinarian and Embrapa researcher Marcos Cláudio Pinheiro, who mostly works with ruminant nutrition, explains that the animals' immune system action is closely related to proteins. "As we provide suitable amounts of protein that meet their nutritional requirements, there is a subsequent improvement in their immune system and ability to reach suitable production levels, even if they are infected." Pinheiro and his team developed diets that are adjusted to provide an increment in metabolizable protein, a type of specialized protein that is effectively absorbed by animals. "With those dietary adjustments, while ensuring theat the animals' nutritional requirements are met, we can reach a suitable level of metabolizable protein to ensure suitable protein absorption, contributing to animal immune defense processes," the researcher says. Thus, if animals are fed correctly, they will be more resilient if they are infested by worms. Photo by: Maira Vergne Paratec Embrapa Goats and Sheep developed Paratec, a national plan to fight animal parasites, which comprises a set of four programs aimed at the control of worms, flies, ticks, scabies and lice. The goal is to have each Paratec program include management strategies for each region, with detailed information to help manage the main parasites of domestic animals. For that purpose, Paratec counts on the participation of researchers and veterinarians from all over Brazil. At the moment, the program for worms, Paratec Vermes, is available, and it provides knowledge and techniques to manage verminosis and drug resistance. The recommendations are aimed at farmers, veterinarians, zootechnicians, technicians in general, and consultants for the sale of veterinary products. The vaccine against worms is another strategy to be integrated into the program recommendations. Economic impacts The occurrence of worms is higher, according to the researchers, in hot and humid places, where it causes high economic losses for breeders, especially due to the high mortality rate it causes in herds. The annual costs of treating only animals affected by Haemonchus contortus were recently estimated at US$26 million, US$46 million and US$103 million for Kenya, South Africa and India, respectively. However, more recent studies have shown that the parasite is present even in colder regions like northern Europe. Animal losses vary a lot across regions, years and seasons, depending on environmental conditions and the effectiveness of control measures. An immediate economic impact is higher when many animals are managed in the same area and when there is a high incidence of the disease. However, production systems with herds raised extensively (on pastures) may be proportionally more affected due to poor animal nutrition, limited access to anthelmintics, and resistance to such drugs.