Department of Primary Industries and Regions, South ...



|March 2018 |

|Contact: Margaret Sexton (08) 8429 0913 |

Poultry Diseases – Tick Fever and Tick Paralysis

Tick fever and tick paralysis are separate problems but will be described together here as they frequently occur at the same time.

TICK FEVER (BORRELIOSIS)

Tick fever is caused by the spirochaete bacterium Borrrelia anserina. The organism is usually transmitted in the bite of an infected fowl tick Argus persicus but it can be spread between birds by ingestion of infective discharges from infected birds. It can be spread mechanically from infected birds by other biting insects but only the tick is its natural host, an infected tick remaining so for well over a year. Fowls that have eaten infected ticks or tick eggs can also contract the disease.

Susceptible species

Most of the domesticated fowl species are susceptible to tick fever. Pigeons and guinea fowl appear to be resistant. Outbreaks have been seen in some wild bird species overseas.

Incubation Period

The incubation period of the disease varies and depends on the mode of infection. When ticks infect a bird, four to nine days elapse before symptoms develop.

Symptoms

In an acute case, the bird becomes depressed, hangs its head, closes its eyes and passes greenish diarrhoea. The bird feels hot to the touch. Wings and legs may be completely or partially paralysed, the comb is dark and death during convulsions follows, usually within 12 hours.

Symptoms in the chronic form of the disease are less pronounced. Generally, loss of appetite, drowsiness and diarrhoea are present, followed by partial paralysis from which the bird may recover.

The paralysis described in both cases is probably tick paralysis (see below) rather than infection with the spirochaete.

Mortality rates in untreated flocks can be high; up to 100% has been recorded.

Diagnosis

The diagnosis can often be based on the clinical picture and the finding of ticks or other heavy infestations of biting parasites.

At post-mortem, the spleen is usually greatly enlarged and has a mottled appearance. The bowel often contains quantities of green mucus with loose contents in the lower bowel.

Laboratory confirmation is made by the use of special stains that reveal the presence of the spirochaete in tissue examined under a microscope.

Treatment

Most antibiotics are effective but penicillin is the drug of choice, one injection often being sufficient to produce a cure in birds not in advanced stages of the disease.

As almost all antibiotics are banned from use in birds producing commercial table eggs, the above advice applies only to non-commercial flocks.

Recovered birds will be immune to reinfection and do not develop a carrier state.

Prevention

There is no longer a tick fever vaccine in Australia so control revolves around adequate control of tick or other external parasites.

The adult parasites do not live on the bird, so when searching for them it is advisable to check all cracks in woodwork by inserting a knife blade or removing timber. Signs of blood indicate that ticks are present. The examination should include roofing timbers, galvanized iron overlaps and loose bark on trees used for perching.

Ticks are extremely hardy and can survive several years without a host. Where sheds are poorly constructed, or birds are not confined to pens, eradication can be difficult.

Control

Parasite numbers can be reduced and controlled but rarely eliminated from housing by spraying insecticide at five-day intervals until thorough inspection fails to detect them. A minimum of three spray applications is necessary (check that the product used is registered for use on poultry and poultry sheds).

TICK PARALYSIS (ACARIASIS)

Tick paralysis occurs only from the bite of the tick and is due to a toxin present in the saliva of the tick. This means that tick fever can occur in the absence of tick but tick paralysis only occurs if ticks are present and feeding.

As the bite of one tick may not be sufficient to cause paralysis, a flock into which ticks have recently been introduced, may become immune before the tick numbers increase. Then when a new flock of birds is introduced, they are faced with high tick numbers and become paralysed and die, while the old flock remains unaffected.

Symptoms

The birds usually begin with partial leg paralysis progressing to complete body paralysis and death. In the intermediate phase, they may try and walk using their wings.

Treatment

There is no treatment but if the birds are examined and found to have large numbers of larval or adult ticks on them, they could be dipped in an insecticide to at least stop any more toxin injection.

Prevention and Control

See as for tick fever.

Author: Dr Kim Critchley, Poultry Health, PIRSA

FOR FURTHER INFORMATION:

Contact your local veterinary practitioner.

IF YOU HAVE SIGNS OF UNUSUAL OR SERIOUS ANIMAL DISEASE*, phone Biosecurity SA Animal Health at Glenside on 82077900, contact your local PIRSA Animal Health officer, call your local veterinary practitioner

OR RING THE DISEASE WATCH HOTLINE: 1800 675 888.

*Signs such as mass mortality events, sudden onset of multiple ill birds, rapid spread of a problem or a noticeably unusual illness in birds.

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