small animals: ectoparasites

Tick toxicosis

Certain species of ticks can secrete noxious substances capable of causing disabling or lethal toxic conditions, termed toxicoses;

Humans and animals might be affected by many forms of tick toxicosis;

• The best known and the most severe tick toxicosis: TICK PARALYSIS;

Ixodes holocyclus info

Eastern Paralysis Tick

Mammals (dogs, cats, horses, humans) birds, reptiles

Most severe form of paralysis of all ticks worldwide

Ixodes holocyclus

was a parasite of monotremes and marsupials but now it can parasitize a wide range of mammals (recorded on up to 34 species): dogs, cats, calves, horses, sheep, goats, pigs, rats, mice etc and birds

A single female tick can kill a dog/cat  up to 17% of the dogs and up to 22% of the cats with tick paralysis die/are euthanized;

Humans: 20 reported deaths;

Ixodes holocyclus: Female morphology

Semi-engorged specimen frequently with body widest just behind coxa IV;

Mouthparts are longer than basis capituli;

Anal groove: anterior position, meet posteriourly;

Ixodes holocyclus: Female IMAGE

Ixodes holocyclus: Male morphology

Females of Ixodes holocyclus at various stages of engorgement (dorsal side)

Females of Ixodes holocyclus at various stages of engorgement (ventral side)

Ixodes holocyclus vs Ixodes cornuatus (Southern paralysis tick)

Females of Ixodes cornuatus have distinct cornua

Ixodes holocyclus: Life cycle

Three host tick

After engorgement the females drop off the host => 2-3 weeks later lay 2000-3000 eggs in the environment

larvae hatch out of the eggs after 1-2 months

The larvae (seed ticks) attach to a host (1st host), feed for 4-6 days then drop to ground => moult to nymphs;

• Nymphs, after hatching attach to another host (2nd host), feed for 4-7 days, then drop to the ground;• After 3-11 weeks the nymphs moult to adults (males or females);

The female ticks attach to another host (3rd host), feed for about 6-21 days (temp dependent) and drop off the host to lay eggs;

Ixodes holocyclus: Life cycle completed

The life cycle is completed within one year in tropical and subtropical areas but usually requires 2 years in temperate years

Ixodes holocyclus: Epidemiology

Geographical distribution

• found mainly along coastal eastern Australia

Isolated cases of tick paralysis far from the areas where ticks are naturally found can occur:

Distribution depends on:

- Humidity

- Presence of natural hosts, bandicoots

- Vegetation

Ixodes holocyclus:

Seasonal distribution

Cases of tick paralyses can occur all year around, but they commonly peak in spring

However, the tick paralysis season (TPS) and the peak will vary with latitude;

The start of the TPS depends on weather conditions in the winter,

Ixodes holocyclus

Number of tick paralysis cases during the tick paralysis season

• The number of cases of tick paralysis is linked to the weather conditions in the summer (December to February) that determines the survival rates of the engorged female ticks and their eggs;

• Warmer and wetter weather conditions than average will lead to an increase in the number of tick paralysis cases;

Ixodes holocyclus

Susceptibility

• Around 10 000 domestic pets along the eastern coast are affected every year;

• No differences between dog breeds with regard to coat characteristics;

• Entire pets (not neutered) more likely to get affected

Ixodes holocyclus: Pathogenesis

• Generally, the female adult tick is responsible for causing paralysis;

A single female tick may cause death of the host;

No correlation between the size of the tick and the severity of clinical signs can produce severe disease/death

Tick virulence might vary with the geographic area, time of the year

Salivary neurotoxins are transferred to the host during feeding;

No detectable amounts of toxin secreted by female ticks until 3rd day of attachment => onset of paralysis symptoms: 3-5 days after attachment;

Ixodes holocyclus: Immunity

• Natural host (bandicoots) survive heavy infestations as a result of acquired immunity rather than having an intrinsic resistance to the toxin;

• Dogs: long term, low dose exposure is required to induce immunity in dogs => it is unlikely urban dogs can acquire a degree of immunity able to confer protection;

Ixodes holocyclus: Clinical signs

• Usually observed 3-5 days after tick attachment

Loss of appetite and voice (laryngeal paresis), lethargy;

Ascending flaccid paralysis: animals become weak in their back legs and ataxic => wobbliness of the hindquarters rapidly worsens so that in a few hours the dog is unable to stand;

Paralysis extends to affect the whole animal which becomes completely limp and flaccid;

There can be drooling, regurgitation, vomiting, coughing;

• Respiration becomes slow and laboured, with a prolonged expiratory phase;

Death occurs from respiratory and cardiovascular failure due to combination of neuromuscular paralysis, pulmonary oedema and/or congestion and central respiratory depression;

• Untreated dogs usually die within 24-48 hours from the onset of the obvious clinical signs;

I. holocyclus: The Tick Lesion

Commonly firm swellings of the skin;

The swelling usually has a central, slightly depressed 1-3 mm scab - when removed it leaves a pit known as a tick crater (long hypostome);

Localisation of Ixodes holocyclus on Dogs

May be found all over the body;

• Common location of ticks: head and body forward of shoulders.

Ixodes holocyclus: Diagnosis

Clinical signs: rapidly ascending flaccid motor paralysis, hoarse-husky type of bark (laryngeal paresis) etc;

Area where I. holocyclus is endemic, previous history of tick paralysis;

Season when the ticks are at peak;

Presence/finding of the female tick(s) and/or tick crater

Search for ticks and tick craters: more than one tick may be present:

(Lack of) Tick prevention:

Ixodes holocyclus: Treatment

1) Remove the tick(s): do not squeeze the tick body;

a) Might not immediately halt the progression of the disease;

b) Clinical signs can appear or worsen in an animal for up to 24 h after removal of a tick

• A thorough search of the animal's coat is highly recommended

2) Administration of anti-toxin serum; 3) Critical care and supportive therapy;

2) Tick Antitoxin Serum (TAS)

Neutralise circulating toxins => effective only in the early stages of the disease => should be given as early in the disease as possible;

Efficacy varies

- animals might develop adverse reactions

Dose rate: debatable but you have to follow the manufacturer’s instructions;

TAS is injected IV slowly: over 20 min

3) Critical care

Oxygen therapy or mechanical ventilation (hypoventilation);

If aspiration pneumonia is suspected => antibiotics;

Ixodes holocyclus prevention: Extremely important

a) Apply acaricides according to the manufacturer's instructions;

b) Thoroughly search animals every day for ticks;

c) Avoid tick (infested) areas, especially in the tick season

a) Apply acaricides according to the manufacturer's instructions;

• Obvious reduction in the number of tick paralysis cases has occurred since the introduction of isoxazolines products

Acaricides commonly used in dogs and cats to prevent tick paralysis

Acaricides for Dogs

1) Phenylpyrazoles

• Fipronil (Frontline original/Frontline Plus: spot-on)

• Fipronil (Frontline: Spray)

2) Isoxazolines

a) Afoxolaner: Nexgard, Nexgard Spectra (oral administration)

b)Sarolaner: Simparica, SimparicaTrio (oral administration)

c) Fluralaner: Bravecto Oral formulations

Bravecto

d) Lotilaner: Credelio, Credelio plus Oral adminstration

3) Pyrethrins and Pyrethroids

a) Permethrin (Permoxin: rinse)

- DO NOT USE FOR CATS

b) Flumethrin

c) Deltamethrin (Scalibor: collar)

It takes 14 days to achieve efficacy higher than 94% against Ixodes holocyclus

4) Formamidines

Amitraz (Preventic: collar)

Acaricides for Cats

1) Phenylpyrazoles

• Fipronil:Frontline(Spray)

• Spray every three weeks;

2) Bispyrazoles

• Tigolaner, Praziquantel and Emodepside (Felpreva)

3) Isoxazolines

• Esafoxolaner, Praziquantel and Eprinomectin: Nexgard Spectra spot-on for cats

• Sarolaner and selamectin: Revolution plus (spot-on)

• Fluralaner: Bravecto (spot-on), Bravecto Plus (Fluralaner & moxidectin)

• Lotilaner:Credelio

4) Pyrethrins and pyrethroids

a) Pyrethrin

b) Flumethrin: Flumethrin and Imidacloprid (Seresto: collar)

Thoroughly check animals every day for ticks

It is unlikely the acaricides confer 100% protection against paralysis tick ->

One tick can cause paralysis -> Check the pets daily for ticks!!

Ixodes holocyclus: infestation of Calves

Ixodes holocyclus kills 10.000 calves every year;

Clinical signs usually occur more than 5 days after ticks’ attachment;

• Treatment with dog antiserum: 4 out of 7 paralysed calves survived;

Ixodes holocyclus: infestation of Horses

Smaller horses are at higher risk

Most ticks attached to the head, neck, axilla, inguinal areas and torso;

Rhipicephalus linnaei (sanguineus) (Brown dog tick)

• Common name: Brown Dog tick (kennel tick);

Specific to dogs (as adults) but it was found on cats, rabbits, rodents, humans etc;

Three host tick (each stage larva /nymphs/adults on another host);

Wide distribution in Australia;

Can transmit many pathogens: Babesia

canis, B. gibsoni, Ehrlichia canis etc;

Rhipicephalus linnaei: Introduction

Rhipicephalus linnaei is unusual among ticks, in that it can complete its entire life cycle indoors;

Because of this, it can establish populations in colder climates  found in much of the world;

Rhipicephalus linnaei: Significance for humans

Rhipicephalus sanguineus has a weak affinity for humans,

Rhipicephalus linnaei (sanguineus): Morphology

Dark brown ticks;

Mouthparts as long as basis capituli;

Basis capituli is hexagonal with lateral angles sharp;

Eyes present, festoons present;

Coxa 1 with two spurs (bifid);

Anal groove: behind the anus;

Spiracular plate: comma shaped;

Two pairs of ventral plates/shields in male;

Rhipicephalus linnaei IMAGE KNOW VENTRAL

Rhipicephalus linnaei IMAGE KNOW DORSAL

Rhipicephalus linnaei (sanguineus): Life cycle

Three host tick;

Female ticks lay eggs in cracks and crevices in houses, garages and dog runs (close to host’s resting place) => larvae => attach and feed on the host for about one week => drop off the host => nymphs => attach and feed on the host for about one week => drop off the host => adults => females attach on a host and feed for up to 3 weeks;

The cycle can be completed in two-three months!!

Rhipicephalus linnaei (sanguineus): Epidemiology

Found world-wide, more commonly in warmer climates (widest geographical distribution among all tick species);

Found on dogs, in kennels and houses, and occasionally on wildlife;

Common in urban and suburban areas => heavy burdens develop on dogs (low abundance on rural dogs);

In temperate areas Rhipicephalus sanguinesus is active mainly from late spring to early autumn;

In warmer areas Rhipicephalus sanguineus may be active all year around;

Predilection sites

Considered a ‘hunter’ tick (emerge from their habitat and move toward their hosts when these animals appear nearby);

Found anywhere on the host skin;

More common between toes and in the

ears;

Rhipicephalus linnaei (sanguineus): Clinical signs

Dogs appear to develop little or no resistance to Rhipicephalus sanguineus re- infestations!

Anaemia in heavy infestations;

Inflamed nodule at site of tick attachment, erythema, pruritus (hypersensitivity), self trauma;

Signs of tick-borne diseases;

Rhipicephalus linnaei (sanguineus): Treatment/control

On dogs: use the acaricides mentioned for Ixodes holocyclus;

Environment of dogs: use of acaricides?

Acaricide resistance: permethrin, deltamethrin and amitraz;