Babesia odocoilei infection in elk

Two male North American elk from a commercial herd were evaluated because of a sudden onset of lethargy, anorexia, and voiding of red urine. These 2 elk were kept in the same pen as 4 other male elk that had died during the preceding 2 months. Laboratory analyses revealed anemia and intraerythrocytic parasites, later confirmed as Babesia odocoilei (a protozoal hemoparasite of cervids). Of the 240 elk remaining in the herd, 59 were screened for B odocoilei by microscopic evaluation of blood smears, protozoal culture of blood, and immunofluorescent antibody testing of serum. Of those 59 elk, 34 (58%) were infected with B odocoilei. Babesia odocoilei infection in elk can be fatal and should be considered in cases of sudden death or acute hemolytic anemia. Familiarity with the disease in elk is essential for practitioners because of the increasing popularity of commercial elk farming.     

Controlling Echinococcus multilocularis-ecological implications of field trials

Two field trials to reduce the prevalence of Echinococcus multilocularis in foxes have been conducted in recent years. Although both trials reduced prevalence considerably, they failed to eradicate the parasite in the study region. Following the control trial in northern Germany, prevalence recovered unexpectedly and rapidly, reaching pre-control levels five quarters (15 months) after the end of control. To understand the internal dynamics of the parasite-host system's reaction to control, we developed a spatially explicit simulation model, Echi. The simulation model incorporates the information available concerning fox tapeworm population dynamics.Using epidemiological parameters to adjust pre-control prevalence, the model predicts the temporal evolution of the prevalence of E. multilocularis in controlled foxes without departing from the range of uncertainty of the field data. However, the model does not predict the rapid pre-control recovery observed in the field trial.The deviation of the model's prediction from field data indicates the involvement of processes not yet taken into account. We modified the model step by step to mimic processes with the potential to cause the rapid post-control recovery of the prevalence of E. multilocularis in foxes.Neither the longevity of tapeworm eggs nor the migratory behaviour of foxes showed any influence on the post-control reaction of the parasite-host system. However, landscape structures leading to a heterogeneous distribution of infected foxes have the potential to alter the system's reaction to control. If infected foxes are concentrated in multiple clusters in the landscape, the model prediction tallied with the range of uncertainty of the field data. Such spatial distribution of infected foxes may be caused by differential abiotic conditions influencing the survival of tapeworm eggs.The model was found to comply best with field data if the foxes acquire partial immunity by being exposed to the fox tapeworm.Both hypotheses explaining the rapid post-control recovery of the prevalence of E. multilocularis observed in the fox population were supported by field data.Both hypotheses have far-reaching consequences for future control trials. The spatial aggregation of infected foxes would enable control efforts to be concentrated on these highly infected areas. However, the acquisition of immunity acts as a buffer to control, necessitating intensified control measures.