Parasite Resistance - CARLA
A saliva test (CARLA) is the tool for determining the genetic basis for resistance to parasites in deer. CARLA represents a powerful potential in the management of parasites of farmed deer.
The infective parasite for both lungworm and gutworm is the third larval stage (L3) on pasture. Once ingested they normally develop to adults and reproduce. The L3 larva has an external sheath which protects it. The sheath is shed after ingestion to allow the parasite to develop. Following exposure to the L3 sheath deer develop antibodies in their saliva. This antibody binds to the sheath significantly reducing the ability to exsheath and develop further. The CARLA saliva test measures the level of this antibody.
We have been testing each crop of our weaners since 2011. Based on the raw data in the last decade the percentage of our weaners with medium/high CARLA in late autumn has gone from 15% to 75%
A significant amount of research resource has focused on CARLA in deer with some very exciting results.
The power of using an eBV rather than just raw data is clearly evident in the our Genetic trend graph as reflected in the sharp rise since CARLA10eBV has been available.
Selecting for early development of immunity to parasites in our deer will not completely replace the need for drench but it is quite conceivable that a goal of significantly less drenching is achievable.
The infective parasite for both lungworm and gutworm is the third larval stage (L3) on pasture. Once ingested they normally develop to adults and reproduce. The L3 larva has an external sheath which protects it. The sheath is shed after ingestion to allow the parasite to develop. Following exposure to the L3 sheath deer develop antibodies in their saliva. This antibody binds to the sheath significantly reducing the ability to exsheath and develop further. The CARLA saliva test measures the level of this antibody.
We have been testing each crop of our weaners since 2011. Based on the raw data in the last decade the percentage of our weaners with medium/high CARLA in late autumn has gone from 15% to 75%
A significant amount of research resource has focused on CARLA in deer with some very exciting results.
- CARLA is a heritable trait (h = 0.45)
- Deer with high CARLA levels have been shown to have lower numbers of adult Ostertagia.
- CARLA affords protection against both lungworm and gutworms (Ostertagia).
- Progeny of high-CARLA sires grow faster and are more profitable than progeny of low-CARLA sires.
- Young high-CARLA deer shed less eggs(gutworm) and larva (lungworm), thus reducing pasture contamination
- CARLAeBV was first developed in December 2016 by Jamie Ward (AgResearch). The CARLA10eBV was incorporated into DeerSelect in 2018.
The power of using an eBV rather than just raw data is clearly evident in the our Genetic trend graph as reflected in the sharp rise since CARLA10eBV has been available.
Selecting for early development of immunity to parasites in our deer will not completely replace the need for drench but it is quite conceivable that a goal of significantly less drenching is achievable.