CHAPTER 30 LEISHMANIASIS: PROTOZOAN DERMATITIS 459
Following inoculation, infection may be eliminated, sequestered in skin and lymph
nodes, or distributed throughout tissues in the body; dogs may be asymptomatic or
symptomatic; estimated 1–5 infected dogs will develop clinical disease.Dogs in endemic areas are continuously exposed; development of disease depends on
the intensity of exposure, parasite virulence, host genetic factors, and the immune
system’s ability or inability to prevent organism replication.Cats: often localizes in skin.
Dogs: invariably spreads throughout the body to most organs; nephrotic syn-
drome/chronic renal failure is the most common cause of death.
Clinical symptoms are due to granulomatous/pyogranulomatous inflammation, depo-
sition of immune complexes, and autoimmunity.
Depletion of infected T cells in symptomatic dogs causes an exuberant B cell compen-
satory response and leads to detrimental hyperglobulinemia with circulating immune
complexes producing indirect damage (e.g., arthritis, uveitis, nephritis, myositis, vas-
culitis) or autoantibodies producing direct damage (e.g., immune-mediated throm-
bocytopenia and glomerulonephritis).Migration of infected macrophages to areas of trauma may encourage localization of
lesions (e.g., pressure points).
Asymptomatic but infected dogs may be inapparent vectors of disease.
Cell-mediated suppression in dogs with leishmaniasis may increase susceptibility
to concurrent infections or disease (including other vector-borne organisms); the
reverse may also be true, producing the increased incidence of disease in older dogs.Incubation period: 3 months to more than 7 years.
SIGNALMENT/HISTORY
Travel to endemic regions inside or outside the United States.
Breed predilection: boxer, German shepherd, rottweiler, cocker spaniel; Ibizan hound
more resistant to symptomatic progression.
Endemic in foxhound kennels in areas of the United States.
Dogs usually less than 3 years of age or greater than 8 years.
Resistance or susceptibility to infection and/or development of clinical symptoms may
depend onLeishmania-specific cell-mediated immunity.
Infection through transfusions of contaminated blood, secretions, venereally, and
transplacental transmission (dog to dog may be the route of transmission in North
America due to lack of a competent insect host).Almost all dogs develop visceral, or systemic, disease; 67–89% have cutaneous
involvement.
CLINICAL FEATURES
Visceral:
Peripheral lymphadenopathy (may be absent in advanced symptomatic cases as
lymphoid tissue is depleted)