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Results for “Tick Paralysis”

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PubMed1995

An evaluation of strategic and threshold control measures against the Karoo paralysis tick, Ixodes rubicundus (Acari: Ixodidae) in South Africa.

Paralysis caused by feeding female Ixodes rubicundus ticks is a major problem in large areas of South Africa. As the life cycle of the tick extends over a period of 2 years, it was hypothesized that strategic treatment of sheep with an acaricide over a 2 year period, timed to kill most engorging females, should markedly lower the biotic potential of the tick. Two flocks of sheep grazing in separate paddocks known to be infested with I. rubicundus were treated either strategically or on a threshold basis (i.e. only when tick challenge exceeded a predetermined critical level in terms of paralysis) for a 2 year period. The tick burdens of untreated control sheep running with the two flocks were monitored over a 4 year period and their seasonal dynamics determined. The times at which peak infestations occurred were similar for both flocks of sheep, but significant differences in mean tick burdens between the two flocks were recorded. Tick numbers on sheep in the strategically treated flock did not decrease during the third and fourth years of the trial as was expected. Possible reasons for this were low stocking densities, especially during times of peak abundance of adults and the presence of wild hosts which maintained tick populations.

Animals↗
PubMed1996

Seasonal dynamics of the Karoo paralysis tick (Ixodes rubicundus): a comparative study on Merino and Dorper sheep.

Karoo paralysis in South Africa is induced in livestock by feeding female Ixodes rubicundus ticks when infestation densities on hosts exceed certain critical levels. It has been shown previously that Angora goats are at a higher risk of being paralysed than Merino sheep, and such differences have been related to differences in feeding behaviour and spatial distribution of the two small-stock breeds. We hypothesized that differences in infestation densities with Karoo paralysis ticks would also occur between Merino and Dorper sheep breeds. A study was conducted under natural conditions in the south-western Free State, to compare infestation burdens of the two sheep breeds and also to investigate seasonal patterns and annual variations in variations in terms of rainfall and temperature. Ten animals of each breed ran free in an area with a known history of Karoo paralysis and were examined on an approximately fortnightly basis, from March 1992 to December 1995, to determine tick abundance. Differences between the two breeds were significant (P < 0.05) during 1992 and 1993, but not during 1994. During the first two years, peak abundance of ticks was reached earlier in Dorper than in Merino sheep, and it also reached higher levels in Dorper than in Merino sheep (mean = 17.9 and 7.3, respectively). In 1993, two Dorper, but no Merino sheep, were paralysed. Dorper sheep are clearly at a higher risk of being paralysed than are Merino sheep, and as such, they can serve as indicators of adult tick activity and hence of the time to commence prophylactic treatment. Differences between the two breeds are probably related to differences in grazing patterns. Marked variation in abundance and the time of onset of peak activity of I. rubicundus occurred over the years. Tick numbers were high in 1993 and 1995, but very low in 1992. In 1993, peak activity occurred earlier (April) than during the other years (June or July). These differences are related to differences in prevailing environmental conditions that influence tick activity in a complex manner. Heightened humidity and lower temperatures during the early stages of seasonal activity of the tick (April or May), normally result in peak abundance of ticks on hosts at that time.

Animals↗
PubMed1980

Tick paralysis in a western harvest mouse.

An engorging female Ixodes pacificus was observed on a western harvest mouse (Reithrodontomys megalotis) in Humboldt County, California. The mouse demonstrated a flaccid paraplegia, but it appeared to recover fully after the tick was removed.

Animals↗