Pediculosis (Stachiella larseni) in farmed mink

Marina Brash, Emily Martin, James D Heal, Hugh Hildebrandt

In early January 2015, a mink producer submitted 2 dead unpelted Sapphire mink with rough hair coats, alopecic skin abrasions (Fig. 1), and chewed tail tips (Fig. 2) to the Animal Health Laboratory for identification of the ectoparasites found on the fur. This same producer had submitted mink less than 2 years previously with the same complaint.

The ectoparasites were identified based on the following taxonomic features:

1) Lice: Order Phthiraptera

2) Biting lice: Head wider than thorax.

3) Suborder Ischnocera: Mouthparts without palps.

4) Genus Stachiella: Host species (mink), 3 segmented antennae without a club, and characteristic body lengths (females 1.1 mm, males 0.8 mm) (Fig. 3).

5) Species: S. larseni. The defining structures included abdominal tergal plates without narrow heavily sclerotized bands and 2 pairs of distinctive anterior dorsal abdominal spine-like setae and sparse fine setae on the rest of the abdomen (Fig. 4). These 2 features distinguished S. larseni from S. ermineae (primarily found on weasels) and S. retusus (primarily found on weasels and martens) that are also less frequently identified on mink.

There is very little information in the literature describing lice from mink, but it is recognized that lice are typically very host-specific and are often found on only one host species, or closely related species. Therefore, these lice are not considered to have originated from dogs. If lice are present on farmed animals, populations may be at low, undetectable levels for most of the year but then usually peak in the winter when animals are kept indoors and close together. The winter of 2014/2015 in Ontario was exceptionally cold for prolonged periods of time. Although the mink were housed in pens inside sheds, this extended cold could have provided sufficient additional stress, especially for colour mutation mink, during a time when the mink were also preparing for the upcoming breeding season.

The quality of the mink pelt is an important factor dictating the value of the pelt, so keeping the ectoparasite burden under control is imperative. Since this farm experienced clinical pediculosis in the recent past, since lice populations can fluctuate widely, and since the farm has been consistently populated with mink for years; it is likely a low level louse population has been present on this farm for a few years.

When considering treatment and control, the life cycle of the parasite needs to be considered given the very short cycle with eggs hatching in ~1 week. The eggs are not affected by insecticides and, since the lice are mostly associated with the animal and less often in the environment, treatment of the animal must be done on a weekly basis. Treatment with permethrin, pyrethrin, or malathion powders in the nest box on a multi-weekly basis should be adequate and if nest box bedding is replaced, it will need to be retreated.

Ectoparasites are not often identified on mink farms but monitoring should still be part of herd management. Considering that quality pelts are the primary product of mink production, external examination during handling times will help identify underlying populations before they impact the health, wellbeing and pelt quality of the mink.   

Evaluating virulence genes and antimicrobial susceptibility of avian pathogenic Escherichia coli from Ontario broiler and broiler breeder flocks 

Michele Guerin, Csaba Varga, Durda Slavic, Patrick Boerlin, Marina Brash, Emily Martin, Rachel Ouckama, Alexandru Weisz, Mike Petrik, Cynthia Philippe, Melanie Barham

Avian pathogenic Escherichia coli (APEC), a subgroup of extra-intestinal pathogenic E. coli, cause diseases collectively named ‘colibacillosis’ in poultry. In broiler chickens, the most common lesions observed on gross postmortem include airsacculitis, pericarditis, perihepatitis, and cellulitis. Colibacillosis causes high morbidity and mortality in broiler chicken flocks, causing extensive economic losses.

The Ontario Animal Health Network (Poultry) reports early systemic bacterial infection in chickens <14 days of age to be very common in Ontario; E. coli is the predominant bacterium isolated, with flock mortality ranging from 1.0 to 15%. Similarly, in broiler chickens >14 days of age, late systemic E. coli infection is the most common diagnosis, with seasonal variation in the number of cases. Cellulitis accounts for a large proportion of chicken condemnations at broiler processing plants in Canada. The objectives of this project are to: 1) identify the most common virulence genes of APEC strains in Ontario broiler and broiler breeder flocks; 2) determine antimicrobial resistance patterns of APEC strains in Ontario broiler and broiler breeder flocks using the disk diffusion susceptibility testing method; and 3) evaluate potential relationships between virulence genes and antimicrobial resistance.

This study will provide baseline data on the virulence genes and antimicrobial susceptibility of APEC strains isolated from clinical cases of colibacillosis in Ontario, which will help to preserve the efficacy of antimicrobials in treating this disease, and which will provide critical information for alternative treatment or prevention, including creating a candidate vaccine to reduce or eliminate infections.

This project (OAHN-02) is funded by the OMAFRA-University of Guelph Strategic Partnership, under the Disease Surveillance Plan, which is a joint federal-provincial Growing Forward 2 project.