Introduction
Poultry current news Tick paralysis or acariasis of poultry is an acute, progressive, symmetrical, ascending motor paralysis caused by salivary neurotoxin(s) produced by certain species of ticks. It occurs only from the bite of the tick and is due to a toxin present in the saliva of the tick. 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.
The toxicity due to tick paralysis is unique, because it is a pulsed toxin flow associated with repeat tick feeding over a set period of time. Birds are generally affected by paralysis, but there are also very odd presentations of associated toxicity.
Etiological agent
The fowl tick, Argas persicus, is found worldwide in tropical and subtropical countries and is the vector of Borrelia anserina (avian spirochetosis) and the rickettsia Aegyptianella pullorum, which causes fowl disease (aegyptianellosis). All stages of ticks may be found hiding in cracks and crevices during the day. Larvae can be found on the birds because they remain attached and feed for 2–7 days. Nymphs and adults feed at night for 15–30 minutes. Nymphs feed and molt several times before reaching the adult stage. Adults feed repeatedly, most commonly under the wings, and the females lay as many as 500 eggs after each feeding. Adult females may live >4 years without a blood meal.
Fig1: Argas persicus tick
Pathogenesis and clinical manifestations
Fowl tick infestation can lead to anemia (most important), weight loss, depression, toxemia, and paralysis. 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. Egg production decreases. Red spots can be seen on the skin where the ticks have fed. Because the ticks are nocturnal, the birds may show some uneasiness when roosting. Death is rare, but production may be severely depressed. Fowl ticks are rarely found in commercial cage-layer operations but may be found in cage-free housing, including breeder, pasture, or small-scale flocks.
Fig 2: Birds showing right eye paralysis due to argas persicus tick infestation
Treatment of tick paralysis in poultry
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. Recovered birds will be immune to reinfection and do not develop a carrier state. After houses are cleaned, walls, ceilings, cracks, and crevices should be treated thoroughly with acaricides using a high-pressure sprayer.
Controlling the larvae is important as it acts as a vector for B. anserina. Repeated treatments with malathion spray helps to reduce the ticks and helps the birds recover. Penicillin injections appear to have no effect in treatment of the bacteria. The elimination of tick larvae is key to reversing the effects of avian spirochetosis. Hydration is also extremely important as death most often results due to dehydration from prolonged paralysis
Prevention
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.
