Topic 1: Introduction to Rickettsia and Chlamydia Flashcards
• List the key differences between the rickettsia and chlamydia
Site of multiplication
Rickettsia: Cytoplasm of cell
Chlamydia: Cytoplasm of cell
• List the key differences between the rickettsia and chlamydia
Mode of replication
Rickettsia: Fission with cross-wall formation daughter cells with infectivity of parent cell
Generation time ~ 18 hrs.
Chlamydia: They have a defined developmental cycle. Infectious elementary body (small infectious form) infects call forms larger reticulate body (that is non-infectious), which divides by fission and is ultimately reorganised to form small progeny elementary bodies.
Generation time ~ 30 hrs.
• List the key differences between the rickettsia and chlamydia
Size
Rickettsia: Size 250 x 600 nm or longer
Chlamydia: Infectious elementary bodies 250 – 350nm diameter.
Non-infectious reticulate body 600 – 1000 nm diameter.
• List the key differences between the rickettsia and chlamydia
Dependence on host cell for energy requirements
Rickettsia: Limited dependence on host cell Chlamydia: Extreme dependence on host
• List the key differences between the rickettsia and chlamydia
Susceptibility to antibiotics affecting 70S ribosome function
Rickettsia: Yes, preferably tetracycline
Chlamydia:
Tetracyclines: yes
Streptomycin: no (bus does prevent absorption to cell)
• List the key differences between the rickettsia and chlamydia
Biological vectors
Rickettsia: Transmitted by arthropods and arthropods are natural host
Chlamydia: Arthropods are not involved in transmission
• List the key differences between the rickettsia and chlamydia
Antigenic characteristics
Rickettsia:
No cross-reaction with chlamydia
No common antigen – species within the same genus often do cross-react antigenically
Chlamydia:
No cross-reaction with rickettsia
The species share common LPS antigens.
- Describe the mode of transmission of the rickettsia and how it differs from chlamydia
Rickettsia
- Multiplies in arthropods such as:
• Insects: lice and fleas
• Arachnids: ticks and mites - Infection occurs through bites
- Special relationship to the Rickettsiales to the blood-forming organs, circulatory system and leucocytes
- Facilitates transfer by biting arthropods
- Describe the mode of transmission of the rickettsia and how it differs from chlamydia
Chlamydia
- Low pathogenicity except when animals are stressed
- Diseases produced can run chronic courses
- Individuals infected for prolonged periods
- Commonly found in:
• Birds
• Humans
• Koalas
• Rumen (sheep & cows)
• Cats
- List the two families within the Rickettsiales and explain how the difference in affinity for cells leads to disease expression
Order: RICKETTSIALES
Family: Rickettsiaceae
- Affinity for lymphoreticular endothelia or leucocytic cells that results in:
• Lymphoreticular hyperplasia (rapid growth proliferation of normal cells that resemble lymph tissue.
• Signs of vascular damage such as haemorrhages or effusion (occurs without an external blow or sudden movement and is related to an inherent or natural defect in the wall of the artery) - Common names for these diseases are:
• Spotted
• Petechial (pinpoint, round spots that appear on the skin as a result of bleeding)
- List the two families within the Rickettsiales and explain how the difference in affinity for cells leads to disease expression
Order: RICKETTSIALES
Family: Anaplasmataceae
- Affinity for RBC
- Associated with damage to RBC resulting in:
• Anaemia
• Haemogloburina
- Be able to explain the clinical signs and distribution of cattle tick fever
Anaplasma marginale (cattle tick fever)
• Clinical Signs
- Mild fever
- Anaemia
- Jaundice
- Can take months to recover
- Can be transmitted by:
• Castration
• Spay
• Multiple use of same instruments/needles
- Be able to explain the clinical signs and distribution of cattle tick fever
Anaplasma marginale (cattle tick fever)
• Distribution
- Northern areas of Australia
• Kimberly’s
• Northern Territory
• Queensland (coastal regions)
- List the chlamydial species endemic to Australia
• Chlamydophila pneumoniae
• Chlamydophila psittaci
- For Aves species:
• Turkeys (ornithine species): omithosis
• Birds (Psittacine species): psittacosis
• Chlamydophila pecorum - Seen in: • Pigs • Koalas • Rumen (sheep & cattle)
• Chlamydophila felis
- Seen in
• Cats
- Describe the main chlamydial diseases seen in Australia including avian chlamydiosis (and zoonotic aspects) and the diseases caused by C. pecorum
• Chlamydophila pneumoniae
– Widespread in koalas but not a significant cause of disease.
– Occasional respiratory disease manifest by rhinitis, coughing,
– Sneezing, serous nasal discharge.
- Describe the main chlamydial diseases seen in Australia including avian chlamydiosis (and zoonotic aspects) and the diseases caused by C. pecorum
• Chlamydophila psittaci
- For Aves species:
• Turkeys (ornithine species): omithosis
• Birds (Psittacine species): psittacosis - C. psittaci seems to have only low pathogenicity and a feature of infections is that clinical disease is often precipitated by stress.
- C. psittaci is zoonotic and considerable care should be taken when handling animals suspected of having a chlamydial disease.
- The principal method of transmission of chlamydia is through direct contact of susceptible animals with infected animals or fomites.
- Inhalation of aerosols containing dried faecal or nasal excrement is also possible.
- Describe the main chlamydial diseases seen in Australia including avian chlamydiosis (and zoonotic aspects) and the diseases caused by C. pecorum
• Chlamydophila pecorum
- Seen in:
• Pigs
• Koalas
• Rumen (sheep & cattle - sporadic bovine encephalomyelitis (SBE)) - Cause of polyarthritis in sheep/lambs (systemic infection of sheep with localisation of organisms in serous membranes)
- Also linked to sporadic and small outbreaks of ovine abortions
- Clinical signs can include fever, in appetence, depression and death but can be vague.
- Calves become uncoordinated and stagger, circle, or fall over objects
- Morbidity rates are most commonly <25%, but can reach 50%.
- The mortality rate can approach 30% and is highest in calves
- Lesions are not limited to the brain; vascular damage can be seen in several organs.
- Describe the main chlamydial diseases seen in Australia including avian chlamydiosis (and zoonotic aspects) and the diseases caused by C. pecorum
• Chlamydophila felis
- Seen in
• Cats - In cats, the incubation period after exposure to an infected cat ranges from 3 to 10 days. Signs can include serous to mucopurulent conjunctivitis, nasal discharge, and sneezing
- Although the disease in cats has been referred to as feline pneumonitis, chlamydiae rarely cause pneumonia in cats.
- Transmission occurs as a result of direct, close contact between cats, because the organism survives poorly in the environment.
- Chlamydial conjunctivitis in cats should be differentiated from conjunctivitis caused by feline herpes virus 1 and feline calicivirus
- Vaccines are available
