Spirochetosis
Spirochetosis in animals generally classified into Blood spirochetosis and Intestinal spirochetosis.
Spirochetosis is a tick borne infection causes both intestinal and blood spirochetosis in poultry.
Avian spirochetosis is an acute, febrile, septicemic, bacterial disease that affects wide varieties of birds.
Etiology
- Borrelia anserina is a helical filiform spirochete with dimensions of approximately 8-20 X 0.2-0.3µm and with 5-8 loosely arranged spirals.
- Their mobility is very high.
Epidemiology
Prevalence of infection
- The disease is limited to tick prevalent area.
- It is prevalent in North Africa, the Middle East, Asia.
- The spirochaetes infects wide variety of birds and mainly occurs in young fowls and adults.
- Different immunological and serotypical B.anserina have been identified in many areas.
- Found in temperate or tropical regions wherein vectors found.
- The most common vector is Argas persicus the “cosmopolitan” fowl tick.
- In the western USA, a highly prevalent vector is A.sanchezi.
Predisposing factors
- A ssociated with deep litter or free range.
- Increased infection in battery management and cage system.
Sources of infection
- Infected droppings are the most important material.
- Infected ticks and infected birds also acts as source of infection.
Transmission
- It is transmitted by the tick, Argas persicus.
- Infection occurs by tranovarian transmission.
- Other vectors such as lice, mosquitoes, ticks, inanimate object mechanically transmit the disease.
- Ingestion of infected fecal droppings, contamination of feed or water, and cannibalism during spirochetemia develops the disease.
Host affected
- Spirochetes affects wide varieties of birds mainly young fowls.
- It is mainly a disease of poultry.
- Young and adult birds are highly susceptible.
- Chickens, turkey, geese, ducks, pheasants, grouse and canaries are affected.
Pathogenesis
- An infected Argas persicus tick transmits the infection while biting animals for blood meal.
- All stages of this tick such as larva, nymph and adult stages maintain the infection F1 larvae are infective in nature.
- Transmits the infection by tranovarian transmission.
- Intestinal spirochetes:
- Mostly associated with litter or free range than battery management and birds in cages.
- It causes morbidity and mortality 100% and mortality 33-75%.
- Death occurs due to infection.
- Recovered birds are immune to homologous type of infection.
Clinical signs
- Incubation period is 3-12 days after tick bite.
- Blood spirochetosis Anorexia, pyrexia, listlessness, depression, somnolence, moderate to marked shivering and increased thirst.
- Cyanosis of head.
- Young birds are affected more severely than older birds.
- Anaemia, diarrhoea and neurological signs.
- Bile-stained faeces observed followed by paralysis which results in death.
Intestinal spirochetosis
- Chronic diarrhoea with wet greasy droppings.
- Reduced egg production of about 10%.
- Reduced egg quality ie., Reduced size, egg weight, carotenoid content, yolk color and shell thickness.
- Delayed egg production.
- Feathers around vent and eggs soiled.
- Caecal content is yellow and or foamy with increased urates excretion.
- Increased thirst.
- Feed efficiency is low leads to growth retardation.
- Progeny of the affected hens may show reduced weight gain and wet droppings.
- Weakness and progressive paralysis.
- The course of the disease is 1-2 weeks.
- Mild strains are common.
- Morbidity can approach 100% and mortality may be 33-77%.
Necropsy Findings
Blood spirochetosis
- Enlarged and mottled spleen is very characteristic.
- Ecchymotic haemorrhages.
- Liver enlarged with small haemorrhages and with necrotic foci.
Intestinal spirochetosis
- No significant gross lesions are seen in affected birds.
- Histologically there is colonization of the surface of the caecum with spirochetes.
- The organism penetrate through the epithelium, especially at the tip of the villi and develop sub epithelial foci.
- Crypts are distended with sloughed epithelial cells. Mucoid enteritis.
Diagnosis
Blood spirochetosis
- Based on clincial signs and necropsy findings.
- Identification of organism in blood.
- Isolation of organism in eggs and in chicks.
- Organism can be grown in embryonated in ducks or chicks embryos in young ones of them.
- Borrelia can grow in Barbour-Stoenner-Kelly medium but the virulence is lost in twelve passages.
- Spirochetes can be identified in stained blood smears using wet blood films and examined under dark-field illumination.
- Examination of interface between buffy coat and plasma by post microhaematocrit spinning method using heparinized blood.
Intestinal spirochetosis
- Clinical signs, absence of gross lesions at necropsy and recognition of the casual organisms by immunofluorescence in scrapings of the caecal mucosa or in droppings.
- Sub inoculation into young chicks, or embryonating eggs, or serological tests have also been described to assist the diagnosis.
Sample collection
- Scrapings from caecal mucosa, droppings, blood and serum.
Differential diagnosis
Prevention
- Vaccines comprising inactivated organisms have been used effectively but many serotypes may exist.
- Vaccines may be prepared from formalin or phenol-inactivated materials, lysates of blood, tissues, embryos, or eggs infected with B anserina , and may be lyophilized or liquid.
- Whole-egg propagated bacterins are usually given in 1 or 2 IM injections.
- Bird s normally have protective immunity after recovering from natural infection.
Control
- Tick control measures.
- Hyperimmune serum unable to reduce the infection in ticks.
- Birds recovered from one type of Borrelia can confers immunity for more than one year for homologous types of infection.
- Reinfection can occurs due to heterologous type.
