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The general order of physical effects occurs in the following manner, usually around 40 to 60 days following infection by the third stage parasite: First, the infected animal has difficulty in maintaining normal stride with both the front and back limbs affected. Unsteadiness on the feet usually follows, with an inability to walk in a straight line. After more time passes, the animal begins to fall quite often. Finally, the animal may become unable to get up at all (Gibbs, 1994; Rickard et al., 1994). To read about other side effects specific to llamas, click here. To read about P. tenuis infections in goats, click here.

After infecting a group of llamas (Lama glama) and a group of white-tailed deer with P. tenuis by harvesting larvae from infected snails, Rickard et. al (1994) conducted a neurological examination, including leukocyte count in cerebrospinal fluid and compared the experimental groups. In all of the llamas, lesions occurred primarily in the central nervous system, especially the spinal cord in both white and gray matter. White-tailed deer did not show lesions in their central nervous systems. This study also found that the day in which clinical signs first appeared was linked with the age of the llama, but after initial infection, age did not play a role in how quickly their neurological function decreased.	Photo courtesy of John Thomas

After infecting a group of llamas (Lama glama) and a group of white-tailed deer with P. tenuis by harvesting larvae from infected snails, Rickard et. al (1994) conducted a neurological examination, including leukocyte count in cerebrospinal fluid and compared the experimental groups. In all of the llamas, lesions occurred primarily in the central nervous system, especially the spinal cord in both white and gray matter. White-tailed deer did not show lesions in their central nervous systems.
This study also found that the day in which clinical signs first appeared was linked with the age of the llama, but after initial infection, age did not play a role in how quickly their neurological function decreased.

Photo courtesy of John Thomas

Image courtesy of T.R. Michels	Samuel et al. (1992) exposed a group of elk calves to varying amounts of P. tenuis larvae. The elk exposed to a larger number of larvae (more than 125) suffered from depression, weakness of limbs, and paralysis before they were killed. The group of elk exposed to the moderate amount of larvae suffered from neurological symptoms, but not all. The elk exposed to the small amount of larvae (approximately 15) did not show obvious neurological signs of infection. These results show that there is a range of elk's neurological responses to P. tenuis infection. However, white-tailed deer can survive infections of up to 500 larvae. Samuel et al. concluded that this shows that white-tailed deer are a more suitable host than elk. Due to the similar responses of llamas (see above) and moose, it can also be concluded that these species are less suitable hosts than white-tailed deer.

Image courtesy of T.R. Michels

Samuel et al. (1992) exposed a group of elk calves to varying amounts of P. tenuis larvae. The elk exposed to a larger number of larvae (more than 125) suffered from depression, weakness of limbs, and paralysis before they were killed. The group of elk exposed to the moderate amount of larvae suffered from neurological symptoms, but not all. The elk exposed to the small amount of larvae (approximately 15) did not show obvious neurological signs of infection. These results show that there is a range of elk's neurological responses to P. tenuis infection. However, white-tailed deer can survive infections of up to 500 larvae. Samuel et al. concluded that this shows that white-tailed deer are a more suitable host than elk. Due to the similar responses of llamas (see above) and moose, it can also be concluded that these species are less suitable hosts than white-tailed deer.