Special Veterinary Pathology

LEPTOSPIROSIS

Synonym : Weil’s disease- Man, Stuttgart disease

Definition

• This is a disease of dogs and large domesticated animals, caused by several species of Leptospira and is of zoonotic importance

Aetiology

• L. icterohaemorrhagiae - Man – weil’s disease
• L. canicola -Dogs. L.pomona – Swine and Cattle
• Goat –L.grippotyphosa

Incidence

• Worldwide distribution and affects cattle, pig, sheep, dog and man
• Rat – Reservoir

Transmission

1. Ingestion 2. Coitus 3. abrasions 4. Intact skin 5. In utero 6. Man can be infected while swimming in water

• Wild animal acts as a carrier
• Outside the body – organism may thrive in water for 3 months.
• Recovered animals may void organism upto 1 year
• Spirochaetes identified by dark field examination of fluid media

Dark field examination- Spirochaetes

• Tissue sections –Organisms are black in colour in silver stains – Levaditi and warthin starry stain

Pathogenesis

• The organism invade the blood stream and multiply producing septicaemia -Temperature rises and last for several days
• Animals not die during this phase, the organisms settles down in liver, kidney and pregnant uterus
• Acute form – Calves, piglets and lambs
• Sheep and goats – encephalitis occurs
• Jaundice – Intravascular haemolysis and hepatic necrosis
• Anemia , icterus, haemoglobinuria
• Leptospires – Found in Urine
• Albuminuria – Interstitial Nephritis- Focal or diffuse
• Gravid uterus – abortion
• Uraemia – Death

Clinicalsigns

Cattle

Acute Subacute chronic

• Septicaemia milder. No Clinical
• High temp icterus symptom
• Petechiae Abortion
• on visible mucous membrane
• Jaundice, anaemia, haemorrhagic mastitis, abortion
• Death within 2 – 7 days

Gross lesions

Acute

• Icterus, anaemia, petechiae on serous membrane
• Liver – Haemorrhages –near the central veins

Miscroscopic lesions

• Liver – Cells shrink and dissociated and separated from sinusoidal epithelium
• Congestion and Haemosiderin crystals within kupffer cells and hyperplasia

Kidney

Gross lesions

• Swollen and red

Microscopic lesions

• Tubular epithelial cell degeneration followed by hydropic degeneration and necrosis

Spleen

• Haemosiderosis
• Acute haemorrhagic meningitis, necrosis of placenta

Subacute

• Interstitial nephritis,infiltration of lymphocytes and plasma cells.
• Placentitis, abortion.
• Leptospira can be found in the foetus.

Sheep and goat

• Peracute: Dullness, abortion and icterus
• Pigs: Abortion, nervous symptoms and focal interstitial Nephritis
• Horses: Periodic ophthalmia – L. pomana
• Dog:
• L. canicola, L. icterohgemorrhagiae
• Dog to dogs, Rats – Dogs
• Kidney -Nephritis
• Liver- Jaundice

Clinical signs

• Peracute: Septicaemia, fever, haemorrhages
• Acute: Fever, anaemia, incraesed ESR and icterus

Gross lesions

• Liver: No lesions may be seen
• Spleen and lymph node – Swollen
• Gastrointestinal tract: Mucosa - Swollen and dark red

Microscopic lesions

• Liver: Hyperchromatic nuclei with eosinophilic granular cytoplasm
• Kidney: Tubular epithelium – Degenerative changes and organisms seen in the tubules
• Gastrointestinal tract : Congestion and petechiae on the mucosa
• Purulent necrotic laryngitis
• Subaute and inapparent – Kidney lesion only observed

Gross lesions

• Capsule peeled off easily

Microscopic lesions

• Focal interstitial nephritis, spirochaetes seen in the tubular lumen as clusters
• L. canicola – Nervous symptoms, purulent lymphocytic meningo encephalitis and gliosis

Diagnosis

• Symptoms
• Demonstration of organisms in the tissue sections
• Microscopic agglutination test
• Inoculation
• Dark field examination of urine