Spirochetosis

Spirochaetosis

Spirochaetosis Also called as Tick Fever or Tick Paralysis Disease was first recorded by Peas (1908) Notifiable disease in poultry

Etiology Borrelia anserina Spiral shaped organisms with 8 – 25 µm in length Stained by ordinary aniline dyes 22 isolates have been found in India 4 main serotypes- W(5), X(3), Y(2), Z(12) IVRI vaccine with W(5) serotype

Host Mainly affects poultry and turkeys May occur in geese, ducks, pheasants, canneries, sparrows and crows Pigeons are relatively resistant

Transmission Important vector borne disease Ticks like Argus persicus and red mite are main vectors Argus persicus can harbour infection for 488 days and transmit infection up to 7 days after feeding on infected blood Trans-ovarian transmission of spirochetes in ticks

Route of infection Tick bite Eating of infected tick by the bird Ingestion of food and water contaminated with excreta of infected bird Smearing of organisms on comb or skin

Clinical signs Incubation period – 3 to 4 days Spirochetes increase in number in blood for 2-3 days and then disappear suddenly Constant or relapsing fever- 43.5 to 44.5 °c Greenish diarrhea Increased thirst, depression, somnolence, loss of appetite Cyanosis of comb

Cont.. Sometimes jaundice may also be seen Inco-ordination and paralytic effect on legs and wings at 5-6 hrs after the onset of symptoms Death with in 12 hrs in acute cases and in 6-8 days in less acute cases, mortality as high as 80 %

Hematological alterations Days post Clinical infection evaluation

Haemoglobin

Leucocytes

1-2

Incubation

Slight anemia

Leucocytosis with neutrophilia

3 -5

Peak

Increase in anemia 25-30%

Increase in neutrophils

5-6

Crisis

Peak of anemia 50%

Leucopenia

6 - 10

Convalencence

Improvement in anemia

Mononuclear leucocytosis

Post mortem lesions Enlarged spleen, mottled because necrotic white pulp appears as grey spots against dark red pulp Distinctly swollen liver with pin point necrotic spots, sometimes liver becomes yellowish green Linear hemorrhages seen between proventricular gland- important lesion Hemorrhagic dermatitis may also be seen

Histopathology Necrosis of germinal centers and hyalinization of the Malphighian corpuscles of spleen Hypertrophy and hyperplasia of reticuloendothelial cells with foamy cytoplasm Liver shows focal areas of necrosis, infiltration of lymphocytes and macrophages in portal areas with occasional focal hemorrhages Hypertrophy of Kuffer cells with foamy cytoplasm Fatty change and hematopoiesis in liver in convalescent birds Necrotic lungs with pneumonic patches Cattarrhal enteritis with mononuclear cell infiltration Perivascular gliosis in brain

Diagnosis Clinical sings Blood smear examination- Stained with Levaditi or Fontana stain Cultural isolation and identification- Inoculation in yolk sac of 6 days old chicken embryo, death of embryo in 9 to 10 days in positive cases, demonstration of organisms in allantoic fluid and embryo blood 2 days post inoculation Serological test: AGPT, FAT Spirochaete immobilization test

Prevention Effective control of ticks and mites Proper disposal of infective carcasses Vaccination: may not be highly successful due to several serotypes *Inactivated Fowl Spirochaetosis Vaccine given at 6th wk of age intramuscularly, immunity lasts for one year.

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