Protozoa III - Leishmania

Question 1

Describe the epidemiology of leishmaniasis.

Answer 1

Major global zoonosis.

• distributed in tropics and subtropics
• in Europe
• endemic Mediterranean areas
• non-endemic areas
• imported and travelling dogs are relevant

Trend towards geographical extension.

Several species in the genus Leishmania
- Leishmania infantum most important
(= L. chagas)

Question 2

Three forms of human leishmaniasis:

Answer 2

a) visceral = kala-azar
b) cutaneous
c) mucocutaneous

Dogs are main reservoir for human visceral leishmaniasis.
Non-clinically infected dogs are the main reservoirs of the parasites.

Question 3

One main form of leishmaniosis in dogs:

Answer 3

• Visceral = viscerocutaneous
  = kala-azar, black fever, Dumdum fever

Non-clinically infected dogs are the main reservoirs of the parasites.

Question 4

Describe leishmaniasis infection in general e.g. hosts, risk factors, IP.

Answer 4

Infection in dogs can be subclinical to fatal.

Cats, horses and other mammals can be hosts.

Risk factors:
- breed (Boxer, Cocker Spaniel, German Shepherd, Rottweiler)
- age (bimodal)
- genetic background

Incubation time: 3 months to 7 years!

Question 5

Leishmania parasites are transmitted by

Answer 5

sand flies

Sandfly - a name for any species or genus of flying, biting and blood-sucking dipteran in sandy areas.

Question 6

Transmission of visceral leishmaniosis.

Answer 6

Vector-borne - female sandflies

Transplacental (vertical)
Blood-transfusion
(Direct contact from dog to dog)

Question 7

Life cycle of Leishmania spp.

Answer 7

Indirect with sandflies.

Sandfly ingests amastigotes from infected host.

Amastigotes transform into promastigotes in fly hindgut, migrate to fly proboscis
and are then transmitted to new host through fly saliva.

In new host, promastigote transforms into amastigote
- hand out intracellular in macrophages
- amastigotes multiply in various other tissues as well.

Question 8

Pathogenenesis of visceral leishmaniosis

Answer 8

Tissue damage caused by the sandfly bite recruits macrophages to the bite.

The leishmania that has been deposited into the bite, is phagocytosed by the macrophages.

Cell-mediated immune response with cytokines leads to killing and clearance of the parasites in mild cases.

In more severe cases, no or only poor cell-mediated immune response is present which allows leishmania present in macrophages to spread around the body.

Note that severe cases will have high serological titers toward leishmania in an attempt to compensate the poor cell-mediated response with a strong humoral response ?

Question 9

Clinical findings and symptoms of visceral leishmaniosis.

Answer 9

Chronic and multisystemic disease.
Incubation period from months to years!!

50-60% are asymptomatic – problem bigger as seems!

Cutaneous signs/ skin lesions – without itching
- chancre - sweating ulcerative lesion
- ears, around the eyes, on the back, legs and tail
- non-itchy diffused alopecia
- hyperkeratosis - head, nose, footpads
- claw hypertrophy

Lymphadenopathy - most frequent sign.
Ocular signs

Apathy, anorexia, anemia, fever
Renal insufficiency
Lameness - muscle and joint lesions

Question 10

define chancre

Answer 10

painless ulcer such as develops in visceral leishmaniasis

(pronounced sh-ahnk) originally french word)

Question 11

Cutaneous signs/ skin lesions found in visceral leishmaniosis are typically distributed where?

Answer 11

• ears, around the eyes, on the back, legs and tail
• chancres / sweating ulcerative lesions
• non-itchy diffused alopecia
• hyperkeratosis - head, nose, footpads
• claw hypertrophy

Question 12

Some non-cutaneous signs of leishmaniasis in dogs.

Answer 12

epistaxis
uveitis
conjunctivitis, blepharitis
cachexia

Question 13

Most important spp. of Leishmania?

Answer 13

L.infantum

Question 14

Lab abnormalities found in dogs with L.infantum infection.

Answer 14

hypoerglobulinemia
hypoalbuminemia

mild to moderate non-regenerative anemia
leukocytosis OR leukopenia

renal azotemia
mild to severe proteinuria

Question 15

Diagnosis of visceral leishmaniosis

Answer 15

Biochemical profile and urinalysis

Serology while there are clinical symptoms – high antibody titers in 80-100% of dogs.

• anti-Leishmania antibodies with IFAT, ELISA, DAT
• NB cross-reactivity with Trypanosoma cruzi

Molecular methods (PCR) from bone marrow, lymph nodes, spleen are most sensitive. * are required for importation to non-endemic countries

Cytology or biopsy (+ Giemsa-staining) for detection of amastigotes.
- lymph nodes, spleen, bone marrow, skin
- NB sensitivity is low!

Question 16

Answer 16

cytology for detection of intracellular and extracellular leishmania amastigotes from a lymph node of a dog with clinical signs

Question 17

Treatment of visceral leishmaniosis

Answer 17

During treatment protocol serology and clinical monitoring should be continued!

Important to control the function of the kidney!

When both liver and kidneys are affected euthanasia is indicated.

drug Allopurinol for long term treatment, per os (risk of xanthine urolithiasis) and animal
may continue to harbor parasites.

drug Meglumine antimoniate is specific leishmaniosis treatment, leishmanicidal, IM injection, toxic.

drug Miltefosine (tradename Milteforan) used in human dermatology and also for dog leishmaniosis, per os.
- Resistance problems

Symptomatic treatment as well.

Vaccine: some effective vaccines exist.

Question 18

Visceral leishmaniosis - vaccination

Answer 18

CaniLeish, Virbac’s canine leishmaniosis vaccine, was launched in May 2011.

“CaniLeish prevented infection in 68.4% of vaccinated dogs, and, in those animals developing active Canine Leishmaniasis, disease progression was lower and generally less severe..”

Question 19

Prevention of visceral leishmaniosis

Answer 19

Because leishmania is transmitted by sand flies, use insecticide collars.

• Scalibor® - Deltamethrin
• Seresto®?? - Imidacloprid and Flumethrin

Use nets in windows.
Limit access of dogs during daytime when flies are active.

After returning from endemic areas – serologically examine the dogs 2x every 3 months.

Question 20

Zoonotic aspect of visceral leishmaniosis

Answer 20

Human visceral leishmaniosis is prevalent in areas where dog leishmaniosis is endemic.

Clinical disease occurs in infants („infantum“), in immunosuppressed people (HIV) and people with malnutrition.

Human infection occurs through sandfly bite, however, dog presence is important as the sandflies pick up leishmania from infected dogs and then leap to people where they deposit the parasite which has been received from the dog (?).