Abstract
The number of Teladorsagia circumcincta 4th-stage larvae in naturally infected lambs from a single farm varied among lambs and among different years. Within each year the distribution of 4th-stage larvae among lambs was similar to that expected from a negative binomial distribution. The ratio of 4th-stage larvae to adult T. circumcincta was low in two years with a low mean intensity of infection but high in two years with a higher mean intensity of infection. The negative binomial distribution is defined by the mean and by k, a parameter that measures dispersion; h was low when mean infection intensity was low but higher when mean infection intensity was high. As h is an inverse index of overdispersion this indicated that the distribution of 4th-stage larvae was more overdispersed at low levels of infection. In a combined analysis, the number of adult T. circumcincta and the plasma IgA activity against 4th-stage larvae were both associated with increased numbers of 4th-stage larvae. There was a statistical interaction between the number of adults and IgA activity that moderated their combined effect.
Original language | English |
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Pages (from-to) | 363-369 |
Number of pages | 7 |
Journal | Parasitology |
Volume | 129 |
DOIs | |
Publication status | Published - Sept 2004 |
Keywords / Materials (for Non-textual outputs)
- Teladorsagia circumcincta
- density dependence
- inhibition
- IgA
- sheep
- OSTERTAGIA-CIRCUMCINCTA
- INHIBITED DEVELOPMENT
- NEMATODE INFECTIONS
- IMMUNE-RESPONSES
- EGG COUNTS
- LAMBS
- RESISTANCE
- POPULATIONS
- AGGREGATION
- PARASITES