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This article was published in 1989
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Elaphostrongylus cervi in Imported Deer and Trichinellosis in Tasmania
Dr. Henry Collins Dept. of Veterinary Pathology, Sydney University
Elaphostrongylus cervi in imported deer
First recorded in this part of the World in NZ in 1975 in Red Deer (Cervus elaphus) and in Wapiti (Cervus canadensis).
The worms live in the connective tissue of muscles
May also be found in the CNS
Long thin brown worms males up to 25mm, females up to 38mm
Now common in NZ
Results of a survey - 16 of 67 farms infected in NI, 22 of 48 farms infected in SI
Especially common in Southland and Fiordland, adapted to cool wet areas similar to N. America, Europe
LC not fully understood
Eggs laid by female worm, hatch to release a L1
By some means the L1 moves to the lungs, enters an alveola then moves up the bronchi and then the trachea, passed out in the faeces.
Survive for 2years or more in soil
Penetrate land snail of species Deroceras panormitanum and D. reticulatum
Develop to L3 in snail in 27+ days
L3 survive in snail up to 2 years
Infected snail ingested, L3 released by digestion, migrates to adult predilection site. Via CNS?
PP about 3mth
Pathogenesis
1. Adults in intramuscular CT
May or may not cause a reaction. If no reaction then difficult to recognise. Reaction: green caseous plaques up to 1.5cm diam.
Draining LNs also affected - greenish mottling.
2. L1 in lungs
Cause a mild interstitial pneumonia, with some consolidation.
Cellular debris and larvae in the bronchi and alveoli
3. Adults in CNS
Not reported to be causing disease in NZ so far
In N.Hemisphere lesions of the CNS cause neurological signs, paralysis - different host species - Reindeer, Rangifer Tarandus caribou and moose Alces alces
It is possible that although there are no reports of neurological disease in NZ, the parasite could have a more severe effect on the exotic species in Australia
Australia is importing deer from NZ in batches of 50 to 80
About 1000 imported so far - Red and Red x Wapiti
Regulations: deer must come from a farm with no history of the parasite. The deer are checked in NZ.
Deer under surveillance in Aust for 100d, during which time 3 faecal samples are examined at 30d intervals
Reason for interval?
Before release treated 2 times with 5d interval with Ivermectin.
There is no follow up.
Only 3 samples have been found +ve in Aust
Better sampling methods may improve detection rate
Diagnosis of infection by Baermann technique. Efficiency?
Need for more efficient test - ELISA?
NOTE: of 300,000 deer slaughtered in NZ in 1987, only 2 carcases had lesions. But how many had worms?
Trichinellosis in Tasmania
NOTE: New agreed name for the disease caused by Trichinella spiralis is trichinellosis (not trichinosis)
Revise LC and epidemiology of T.spiralis
Sequence of events:
In July 1987, 3 spotted-tailed quolls that had been found dead or moribund, in the vicinity of the Cradle Mountain Lodge, were examined at the Mount Pleasant Laboratory. A nematode infection was noted in the muscles of one quoll, that was subsequently identified as trichinellosis, caused by the parasite Trichinella spiralis.
From June 1988, further animals were trapped from around the area where the quoll was found, and the muscles examined by a digestion method. Larvae were found in:
12 of 17 (70%) Tasmanian Devils, Sarcophilus harrisii
3 of 10 (30%) Spotted-tailed quolls, Dasyurus maculatus
8 of 22 (36%) Eastern Quolls, D. viverrinus
and a low level of infection in Brush-tailed possums, Trichosurus vulpecula.
Some of the animals were trapped 40Km from the Cradle Mountain Lodge.
No infection was found in Bennett's Wallabies, Tasmanian Pademelons, Rats (R. rattus), mice (M. musculus), or feral cats. It appeared likely, at first, that the parasite had been introduced to Tasmania by foreign tourists. Wild animals are commonly fed at the Lodge in the National Park.
However further surveys showed that infection was not confined to the National Park, but is common in wildlife all over the state.
Of 136 Devils examined, 40 (29%) were infected.
A retrospective examination of museum specimens showed infection in Devils and Quolls dating from as far back as 1976. So the parasite has probably been in Tasmania for a long time.
The presence of this important parasite in Tasmania in Australia obviously had important implications with regard to the export of pig meat and with regard to the movement of animals from Tasmania to the mainland.
Following the initial finding, many more animals were examined.
Nothing was found in 1,768 pigs from 149 properties. On the Mainland 100,000 horses and 90,000 feral pigs have been tested since the mid '70's, all negative. Following the finding in Tasmania, more than 3,500 diaphragms from farmed pigs on the Mainland have been tested with negative results.
Experiments showed that rodents, pigs and chickens could be infected with the parasites from the Tasmanian animals, but that the parasite is not very infective for placental mammals.
Samples were sent to Canada to be identified by DNA fingerprinting.
Result, hot off the press! It is not T.spiralis but a closely allied parasite T. pseudospiralis.
This parasite is found in several countries USSR, India etc. in wildlife, including birds (explaining why it was transmissable to chickens).
This species differs from T. spiralis in that there is no cyst wall around the larva in the muscle.
However it has been shown to infect rats and monkeys. In monkeys it produces a similar disease to classic trichinellosis.
Can it infect humans? It seems likely.
T.spiralis is most commonly transmitted from prey to predators, or acquired by scavenging. The animals most commonly infected in Tasmania, Devils and Quolls, are efficient scavengers. Some possums occasionally eat carrion. Apparently the transmission of the parasite has been confined to this sylvatic cycle and thus remained undetected until now.
So far there has been no attempt to ban meat from Tasmania, the screening procedures are thought to be adequate.