TY - JOUR

T1 - Disease transmission in an extreme environment: Nematode parasites infect reindeer during the Arctic winter

AU - Carlsson, Anja M.

AU - Irvine, K. Justin

AU - Wilson, Kenneth

AU - Piertney, Stuart B.

AU - Halvorsen, Odd

AU - Coulson, Stephen J.

AU - Stien, Audun

AU - Albon, Steve D.

PY - 2012/7

Y1 - 2012/7

N2 - Parasitic nematodes are found in almost all wild vertebrate populations but few studies have investigated these host-parasite relationships in the wild. For parasites with free-living stages, the external environment has a major influence on life-history traits, and development and survival is generally low at sub-zero temperatures. For reindeer that inhabit the high Arctic archipelago of Svalbard, parasite transmission is expected to occur in the summer, due to the extreme environmental conditions and the reduced food intake by the host in winter. Here we show experimentally that, contrary to most parasitic nematodes, Marshallagia marshalli of Svalbard reindeer is transmitted during the Arctic winter. Winter transmission was demonstrated by removing parasites in the autumn, using a novel delayed-release anthelmintic bolus, and estimating re-infection rates in reindeer sampled in October, February and April. Larval stages of nematodes were identified using molecular tools, whereas adult stages were identified using microscopy. The abundance of M. marshalli adult worms and L4s increased significantly from October to April, indicating that reindeer were being infected with L3s from the pasture throughout the winter. To our knowledge, this study is the first to experimentally demonstrate over-winter transmission of a gastro-intestinal nematode parasite in a wild animal. Potential mechanisms associated with this unusual transmission strategy are discussed in light of our knowledge of the life-history traits of this parasite.

AB - Parasitic nematodes are found in almost all wild vertebrate populations but few studies have investigated these host-parasite relationships in the wild. For parasites with free-living stages, the external environment has a major influence on life-history traits, and development and survival is generally low at sub-zero temperatures. For reindeer that inhabit the high Arctic archipelago of Svalbard, parasite transmission is expected to occur in the summer, due to the extreme environmental conditions and the reduced food intake by the host in winter. Here we show experimentally that, contrary to most parasitic nematodes, Marshallagia marshalli of Svalbard reindeer is transmitted during the Arctic winter. Winter transmission was demonstrated by removing parasites in the autumn, using a novel delayed-release anthelmintic bolus, and estimating re-infection rates in reindeer sampled in October, February and April. Larval stages of nematodes were identified using molecular tools, whereas adult stages were identified using microscopy. The abundance of M. marshalli adult worms and L4s increased significantly from October to April, indicating that reindeer were being infected with L3s from the pasture throughout the winter. To our knowledge, this study is the first to experimentally demonstrate over-winter transmission of a gastro-intestinal nematode parasite in a wild animal. Potential mechanisms associated with this unusual transmission strategy are discussed in light of our knowledge of the life-history traits of this parasite.

KW - Experiment

KW - Parasite–host interaction

KW - Over-winter transmission

KW - Svalbard reindeer

KW - Marshallagia marshalli

U2 - 10.1016/j.ijpara.2012.05.007

DO - 10.1016/j.ijpara.2012.05.007

M3 - Journal article

VL - 42

SP - 789

EP - 795

JO - International Journal for Parasitology

JF - International Journal for Parasitology

SN - 0020-7519

IS - 8

ER -