Chlamydiosis or Psittacosis

Chlamydiosis or Psittacosis is a term used to indicate the disease in psittacine birds, humans and animals.

Ornithosis: Disease affecting birds other than psittacines.

Etiology

• C. trachomotis– mainly humans and other mammals.
• C. psittaci- humans, mammals and poultry.
• C. pneumoniae- humans.
• C. pecorum- ruminants and other mammals.

Chlamydia psittaci is a gram negative, coccoid organism and has a distinct life cycle. The organism has obligatory type of replication intracellularly within the cytoplasmic vacuoles of eukaryotic cells.

Epidemiology

Prevalence of infection

• C. psittaci prevails in psittacine birds and is endemic in tropical and subtropical region especially South America, Australia and in feral pigeons in many parts around the world.
• World wide in distribution.
• In poultry it is occasionally epidemic in nature.
• Sporadic
• occurrence of the disease noticed in flocks.
• Mortality reach 0-30%.

Predisposing factors

• Stress due to migration, transportation, changes in diet / environment, concurrent infection with other organisms such as Salmonella or Pasteurella multocida.

Sources of infection

• The infectious elementary body is highly resistant outside the host and so able to survive in dried excreta and in manure for longer periods.
• The organism is destroyed in putrified carcasses.
• Elementary bodies found in feces and respiratory secretion.

Transmission

• Transmission Directly – Close contact
• Indirect – Fomites, biting insects, mites and lice
• Mainly by inhalation – Infected dust
• No transovarian transmission

Host affected

• Turkeys are highly susceptible.
• Ducks, pigeons and chickens are rarely affected.
• Wild birds are affected by less virulent strains.
• Young birds are more susceptible than older birds.
• Psittacine birds, ducks and turkeys cause severe infection in humanbeings.

Pathogenesis

During multiplication of the organism within the eukaryotic cells two inclusion bodies are produced:

1. Elementary body:
   • A small, infectious form, measures 250- 300 nm diameter which is surrounded by a rigid walled.
2. Reticulate body:
   • A larger, non infectious form, measures 400- 600 nm diameter, flexible walled, develops from a small elementary body.
   • Reticulate body divides by binary fission and produce daughter elementary bodies.
   • These daughter elementary bodies attaching to the cell membrane of the host and undergo maturity before they rupture.
   • On rupture the inclusion bodies libearated from the host. Inclusions able to survive outside of the host for long time until they acquire another host.

• The entire process of life cycle is being completed in 28-32 hours.
• The organism gain entry through inhalation reaches various organs, such as lungs, air sacs and under obligatory mode of replication within the cytoplasmic vacuoles in the euakryotic cells.
• Via the haematogenous route spread into pericardium, liver, spleen and kidney where in the organism undergo further multiplication and produce elementary bodies and reticualte body.
• Incubation period varies upon factors such as virulence, the host species affected, age of the host and it may be 5- 60 days.

Clinical signs

• Mild to severe form of disease occurs in turkeys, ducks, pigeon.
• Depression, ruffled feathers, anorexia, purulent nasal exudate and conjunctivitis.
• Tracheitis, rales, grey-green diarrhoea, occassionally droppings may be gelatinous with blood.
• Nervous signs:
  • In ducklings, trembling and an unsteady gait noticed.
  • Pigeon affected by temporary ataxia.
  • Chickens are rarely affected.

Necropsy Findings

• The development of lesions varies depends on the severity and acute nature of the disease.
• Serosal surfaces covered by serofibrinous exudate.
• Pericarditis, congestion of lungs and cloudiness of wall of the air sac.
• Enlargement and softening of liver, spleen with small necrotic foci and petechiation noticed.
• In pigeons spleen may rupture.

Diagnosis

• Clinical signs and gross lesions.
• Confirmation by demonstration of causal organism or its isolation, identification and serological examination of paired sera.
• Wrap carcass for laboratory.
• Examination should be made in bio hazard cabinet.
• Demonstration of casual organism.
• Direct smear examination
• Demonstration of chlamydial antigen and sera.
• Demonstration of chlamydial DNA.
• Culture and identification of organism.
• Direct smear examination
• Smear from exudate, lesion on the surface of liver or spleen, cloacal, tracheal, conjunctival swabs stained by modified Ziehl-Neelsen stain. Elementary bodies stain red while the back ground is blue-green
• Giemsa, Machiavello, Castanada and an Iodine technique also used.
• Direct smear examination identifies only elementary bodies and so they lack sensitivity.
• Demonstration of inclusion bodies by inoculation into embryonated eggs, tissue cultures and mice inoculation.
• Demonstration of Chlamydial Antigen
• Verification  of  specific Antigen.
• Fixed infected tissue processed for FAT or IPT.
• Identification of Chlamydia after growth in eggs or cell culture

Sample collection

• Tissues, exudates and feces collected in diluent containing antibiotics, which reduce contaminants but have no adverse effect on Chlamydia.

Differential Diagnosis

• Borreliosis
• Pasteurellosis
• Salmonellosis
• Infectious laryngotracheitis

Treatment

• Chlortetracycline, in turkeys- 200-800 g / ton of feed or 0.2-0.4 gm in one litre of drinking water.
• Doxycycline by oral route for complete elimination of infection.
• Medicated corn, mash diets with 1% chlortetracycline (CTC) and 0.7% calcium.
• White millet seed with 0.5 mg CTC/g of seed, for budgerigars, parakeets and finches only for 30 days.
• A special diet is necessary for lories and lorikeets, which feed on nectar and fruit in the wild.
• Doxycycline 40-50 mg/kg body weight by oral once a day for cockatiels, cockatoods and parrots.
• Doxycycline 75-100 mg/kg body weight IM for every 5-7 days for the first 4 weeks.

Prevention

• Prohibit sale of infected birds.
• Avoid addition of birds to cages with other healthy birds.
• Prevent contact of any birds with the public and other birds.

Control

• Follow the directions issued by the local health officers.
• Place the birds under antibiotic treatment with environmental cleaning and sanitization.
• Destroy all infected birds followed by environmental cleaning and disinfection.
• Iodophore, formaldehyde and many other sanitizers can be used to eliminated both inclusion bodies from the environment.
• Provision of medicated feed.
• Monitoring of feed consumption.