Immuntest på slædehund - priktest studiet (engelsk)

Polluted Minke Whale Blubber (Balaenoptera acutorostrata) Impair Cellular Immunity in <st1:place w:st="on">West Greenland</st1:place>  Sledge Dogs (Canis familiaris) (Environ Sci Technol 40:2056-2062)

Abstract

Minke whale (Balaenoptera acutorostrata) blubber is rich in organohalogen contaminants, mercury and n-3 fatty acids. In the present study we show that a daily intake of 50-200 g minke whale blubber causes an impairment of the non-specific and specific cellular immune system in the <st1:place w:st="on">West Greenland</st1:place> sledge dog (Canis familiaris). Immune reactions were measured by mitogen (PHA = Phytohaemaglutinin, Con A = Concavalin A) and antigen (KLH = Keyhole Limpet Haemocyanin) intradermal testing. The study used exposure levels similar to those of Inuits and polar bears and it is therefore reasonable to infer that Inuits and polar bears may suffer from similar decreased resistance to diseases. It is speculated that food sources are depleted by thinning sea ice due to climate change, why more research should assess the forecasted rise in additive immunopathy effects in polar bears and other Arctic top predators. Additionally, our study suggests that the fatty acid composition may be of importance when investigating combined immuno toxic effects of contaminated food resources in future Inuit and polar bear studies.

Aim of study

The aim of the immunizational trial was to study the cell-mediated immunity expressed via intra dermal testing. Pups were intradermally tested at 18 (exposed) and 21 (controls) weeks of age. The parent (P) and offspring (F) generation were followed for up to 52 and 21 weeks, respectively. It is noteworthy, that the pups also received organochlorines and brominated flame retardents transplacentally and via milk in their first 8 weeks of life.

Experimental design

The experimental design was conducted as a randomized blind intervention study on West Greenland sledge dogs (Canis familiaris) in Aasiaat, <st1:PlaceName w:st="on">Disco</st1:PlaceName> <st1:PlaceType w:st="on">Bay</st1:PlaceType> , <st1:place w:st="on">West Greenland</st1:place> using real life exposure and taking seasonal fasting from yearly climatic oscilliations into account. The parent generation (P) was composed of an exposed and a control group (8 bitches in each) and their 9 pups (4 exposed and 5 controls, - all siblings). The exposed group was fed 50-200g per day of organochlorine and mercury contaminated <st1:place w:st="on">West Greenland</st1:place> minke whale (Balaenoptera acutorostrata) blubber. The control group was fed pork fat (extremely low in both organochlorines, mercury and polyunsaturated fatty acids). Bitches were fed exposed and control feed respectively, immediately after entering the project at age two months, while pups were fed exposed and control feed, respectively, immediately after weaning. All dogs were kept in chains but exercised regularly, investigated routinously by a field veterinarian and immunized for canine distemper virus, parvo virus, hepatitis virus, parainfluenze virus and rabies. To minimize genetic differences between the groups, all 16 bitches were paired sisters placed within each group. They were fed equal amounts of standardized Royal Canin dry dog pellets (50-200g/day) to cover basic nutrients and microelements.

Intra dermal in vivo field testing

To characterise the effect of OHC exposure on the cell-mediated immunity, intra dermal in vivo stimulation (delayed hypersensitivity; type IV) with mitogens (PHA and Con A; unspecific induced lymphocyte proliferation) was applied to 16 bitches. The same mitogens and an antigen (KLH; specific T lymphocyte response following immunization) was applied to 9 pups. The intradermal test was applied to an 5 x 10 cm area laterally on the thorax. Local anesthetics or sedatives were not used. Four weeks prior to the intradermal test, all pups were immunized at 14-17 weeks of age subcutaneously with 1 ml antigen (Keyhole Limpet Hemocyanin).

The intradermal tests were performed by application of 0.1 ml Phytohaemaglutinin-P, Concanavalin A, as mitogens, and KLH as antigen. Only the F1 generation was tested with KLH in two concentrations and both generations were tested with PHA and Con A in two concentrations. 0.1 ml (s.i.c.) 0.9% NaCl was used as a negative control.

Wheal size (diameter, height and erythema) was mesured at 24 and 48 hour delayed type 4 hypersensitivity (48 hour reactions were excluded from the analyses as all these were magnitudes lower than the 24 hour reaction). Analyses of organochlorines and brominated flame retardents were conducted at The National Wildlife Research Centre, <st1:place w:st="on"><st1:City w:st="on">Carleton University</st1:City> , <st1:country-region w:st="on">Canada</st1:country-region></st1:place> . The animal experiments were performed on a licence granded by the Home Rule Government of Greenland.