The recent transmission of brucellosis from elk back to cattle in Idaho and Wyoming illustrates how the area, as the last remaining reservoir in the United States, may adversely affect the livestock industry. Eliminating brucellosis from this area is a challenge, as many viewpoints exist on how to manage diseased wildlife. However, the Wyoming Game and Fish Department has recently begun to protect scavengers (particularly coyotes and red fox) on elk feedgrounds, because they act as sustainable, no-cost, biological control agents by removing infected elk fetuses quickly.The National Elk Refuge in Jackson, Wyoming asserts that the intensity of the winter feeding program affects the spread of brucellosis more than the population size of elk and bison. Since concentrating animals around food plots accelerates spread of the disease, management strategies to reduce herd density and increase dispersion could limit its spread. Effects on hunters
Hunters may be at additional risk for exposure to brucellosis due to increased contact with susceptible wildlife, including predators that may have fed on infected prey. Hunting dogs can also be at risk of infection. Exposure can occur through contact with open wounds or by directly inhaling the bacteria while cleaning game. In some cases, consumption of undercooked game can result in exposure to the disease. Hunters can limit exposure while cleaning game through the use of precautionary barriers, including gloves and masks, and by washing tools rigorously after use. By ensuring that game is cooked thoroughly, hunters can protect themselves and others from ingesting the disease.
Each miracidium goes through several developmental stages inside the snail: firstly into a series of daughter cells called sporocysts and then into rediae, which give rise to many worm-like larvae called cercariae. The cercariae penetrate through the body of the snail, emerging into the water. Development in the snail takes about 9 to 13 weeks.The cercariae then infect the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. Encystment occurs in the liver, gills, intestine, skeletal muscles and sometimes in the heart. These cysts are the infective stage for the mammalian host. Freshwater crab species of genera Potamiscus, Potamon, Paratelphusa, Eriocheir, Geothelphusa, Barytelphusa, crayfish species of genus Camberoides and shrimps of genera Acrohrachium and Caridina commonly serve as the secondary intermediate hosts. The secondary intermediate hosts are infected either by directly eating the snail or penetration of the body by free-swimming cercariae.Human infection with P. westermani — the best understood species — occurs by eating inadequately cooked or pickled crab or crayfish that harbour metacercariae of the parasite. The metacercariae excyst in the duodenum, penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5 to 12 mm by 4 to 6 mm). Unlike most other trematodes, after they migrate from the intestine, they remain in the peritoneal cavity until they find a suitable partner. Only then do the couples enter the lung tissues to form capsules.