The clinical features of Leishmaniasis vary widely due to the numerous pathogenic mechanisms of the disease process, the different organs affected and the diversity of immune responses. Clinical disease is associated with a marked antibody response that does not confer protection. In fact, immune-mediated mechanisms are responsible for much of the pathology in canine Leishmaniasis. The spectrum of disease can range from sub-clinical to rapidly fatal.

After a variable incubation period (up to seven years in some cases), the disease manifests in a range of forms, including cutaneous and visceral syndromes. Skin lesions are seen in 80%–90% of clinically affected dogs, lymphadenomegaly in 62%–90%, ocular disease in 16%–81%, splenomegaly in 10%–53%, and abnormal nail growth (onychogryphosis) in 20%–31%.

Clinical disease due to L. infantum commonly includes one or more of the following:

• Exfoliative dermatitis, which can be generalized or localized over the face, ears, and limbs.
• Ulcerative, nodular, or mucocutaneous dermatitis that may be associated with considerable bleeding.
• Papular dermatitis may be seen in mild cases of disease,
• Ocular abnormalities (including keratoconjunctivitis and uveitis),
• Epistaxis
• Weight loss,
• Exercise intolerance,
• Lethargy.

Other clinical findings may include polyuria and polydipsia due to kidney disease, vomiting, colitis, melaena, and lameness due to joint, muscle, or bone lesions. Sole presenting signs of disease could be epistaxis, ocular abnormalities, or manifestations of kidney disease without skin abnormalities.

• Clinical laboratory findings may include:
• mild to moderate nonregenerative or, more rarely, regenerative anaemia
• thrombocytopaenia
• serum hyperproteinaemia with hyperglobulinemia and hypalbuminaemia, frequently expressed by a decreased albumin:globulin ratio
• increased liver enzymes or azotaemia are found in some infected dogs.

Laboratory investigation of a suspect case of Leishmaniasis is undertaken at the Australian Centre for Disease Preparedness (ACDP) and definitive diagnosis with differentiation of exotic Leishmania spp. from endemic L. (Mundinia) macropodum and potentially other Australian Leishmania spp. via species-specific tests, such as polymerase chain reaction (PCR) and sequencing.

The sensitivity of commonly used diagnostic tests is poor in animals with sub-clinical Leishmaniasis. Negative test results in such animals do not indicate freedom from infection.

Owners of exposed animals should be advised that infection may still be present (but undetectable), and that clinical disease could develop up to seven years after the last potentially infectious exposure.

An animal is a suspect case where:

• serological results indicative of Leishmania infection or
• Leishmania spp. identified histologically or cytological smears or
• clinical signs are consistent with Leishmaniasis or
• there is epidemiological evidence that the animal has been exposed.

An animal is a confirmed case where:

• a polymerase chain reaction (PCR) positive assay on diagnostic samples (e.g. blood, bone marrow, lymph node aspirates, conjunctival swabs or skin biopsies) or
• positive culture of the particular Leishmania spp. (however this is not routinely conducted).

Leishmaniasis is spread to dogs via bites from infected phlebotomine sandflies

Most Leishmania species are zoonotic. Dogs infected by L. infantum are considered the main sources of human Leishmaniasis worldwide. In endemic areas, leishmania is predominantly transmitted to humans via phlebotomine sandflies that have fed on a clinically infected vertebrate, commonly dogs. Rare cases of iatrogenic transmission (needlestick) and infection following blood transfusion have been reported. Veterinarians investigating potential Leishmaniasis cases should take precautions to reduce the likelihood of direct transmission.

The likelihood of people acquiring infection in Australia is considered very low. None of Australia’s phlebotomine species are recognised pests of humans and the specific species of phlebotomine sandflies that have been identified as biological vectors for Leishmania spp. elsewhere in the world have not been found in Australia. Whether competent vectors for transmission of Leishmaniasis to humans exist in Australia is unknown. Investigations carried out in response to post-quarantine detections of L. infantum in imported dogs in have revealed no evidence of local transmission from these cases.

The only known endemic Leishmania spp. in Australia is L. (Mundinia) macropodum. To date, it has not been associated with disease in humans or in domestic animal species.

Advice to owners

Owners of a confirmed case of leishmaniasis should be informed that an investigation by a Local Land Services veterinarian will be conducted to determine the likely source of infection and to identify other animals that may have been exposed. Exposed animals may include:

• dogs sourced from the same overseas kennel as infected dogs
• companion dogs of infected dogs
• bitches mated with infected dogs, or inseminated with semen from an infected dog
• offspring of infected bitches
• dogs that have received blood transfusions or bites from infected dogs

Testing of other exposed animal species may be considered if vector transmission to dogs is suspected or demonstrated.

Private veterinary practitioners should discuss with the owner:

• the zoonotic risk and recommend that they contact the Public Health Unit of their Local Health District (1300 066 055) for further advice on protecting themselves from infection
• the prognosis
• the options for treatment of the animal, including drug therapy to reduce parasitaemia, use of impregnated collars to inhibit bites from potential biological and mechanical insect vectors
• desexing to prevent breeding, and
• euthanasia of the dog which may be considered for both animal welfare and disease management reasons.

Owners are responsible for:

• Mitigating spread risk and managing contacts between infected animals and other animals or vectors.
• Adhering to the agreed upon management plan
• Monitoring the dog following treatment for signs of clinical relapse and seeking veterinary advice promptly if concerned.
• Covering all costs associated with:
  • Desexing
  • Any veterinary treatment
  • Ongoing testing
  • Euthanasia of the animal if the owner elects that course of action

NSW DPIRD Biosecurity & Food Safety will cover the following costs:

• Initial testing of animals with suspected leishmaniasis.
• Testing of in-contact animals.
• Courier charges to submit the above samples to EMAI.

• Primefact - Leishmaniasis - Information for veterinarians PDF, 236.98 KB
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