(EXAM 2) Lecture 9: Eye and ear infections- II

What is conjunctivitis caused by Chlamydiae?

An acute, chronic, or recurrent infection of the conjunctiva caused by intracellular bacteria from the family Chlamydiaceae.

What are the clinical signs of chlamydial conjunctivitis?

Often asymptomatic but can cause acute or chronic purulent inflammation of the conjunctiva, sometimes with keratitis or other pathologies.

What type of bacteria cause chlamydial conjunctivitis?

Intracellular bacteria from the family Chlamydiaceae.

Why is systemic antibiotic treatment preferred for chlamydial conjunctivitis?

Because chlamydial conjunctivitis may result from systemic infection and/or involve bacterial shedding at other anatomic sites.

Which anatomic sites can Chlamydiae infect aside from the conjunctiva?

The mucosa of the gastrointestinal tract, reproductive tract, and conjunctiva.

What is the significance of systemic infection in animals with chlamydial conjunctivitis?

Animals are typically infected systemically, leading to potential pathology and bacterial shedding at multiple anatomic sites.

What class of antibiotics is typically used to treat chlamydial conjunctivitis?

Tetracycline-class antibiotics.

Which Chlamydia species cause conjunctivitis in different host species?

Chlamydia caviae → Guinea pigs

Chlamydia suis → Pigs

Chlamydia psittaci → Birds, sheep

Chlamydia pecorum → Cattle, sheep, pigs, ruminants (e.g., reindeer), and wildlife (e.g., koalas, crocodiles)

What is the most common cause of pinkeye in sheep?

Chlamydia pecorum.

What are the general characteristics of Chlamydiae?

Spherical intracellular bacteria with a unique developmental cycle.

Which stains are used to identify Chlamydiae?

Modified Ziehl-Neelsen (MZN) and Giemsa stains.

Why are Chlamydiae considered energy parasites?

They cannot synthesize ATP and rely on host cells for energy.

What are key structural features of Chlamydiae cell walls?

No peptidoglycan but contain family-specific lipopolysaccharides (LPS).

What are the key properties of Elementary Bodies (EBs)?

Infectious, extracellular, and metabolically inactive.

Do Elementary Bodies (EBs) multiply?

No, they do not multiply.

Why are EBs considered the infectious form?

They are small, resistant to environmental stress, and facilitate transmission between hosts.

What are the key properties of Reticulate Bodies (RBs)?

Non-infectious, intracellular, and metabolically active.

Do Reticulate Bodies (RBs) multiply?

Yes, they multiply inside host cells.

Why are RBs considered the reproductive form?

They grow and divide intracellularly before transforming back into EBs for release.

What is the causative agent of feline chlamydiosis?

Chlamydia felis (formerly feline Chlamydia psittaci).

What clinical conditions are associated with Chlamydia felis in cats?

Primarily conjunctivitis, less commonly rhinitis.

Why is "feline pneumonitis" a misnomer for feline chlamydiosis?

Because lower respiratory tract infection caused by C. felis is rare.

How is Chlamydia felis transmitted?

Direct or indirect contact with conjunctival or nasal secretions; may also be shed from the reproductive tract.

Which cat populations are most at risk for infection?

Multi-cat households, breeding catteries, and cats under 1 year of age.

What is the incubation period for feline chlamydiosis?

~5 days

What are the primary ocular signs of C. felis infection?

Unilateral or bilateral conjunctival congestion, clear ocular discharge, chemosis, and blepharospasm.

How does secondary bacterial infection affect the disease?

Secondary infection with Mycoplasma felis or Staphylococcus spp. can cause mucopurulent ocular discharge.

What respiratory signs may accompany conjunctivitis?

Sneezing and nasal discharge.

How long does feline chlamydiosis typically last?

It resolves within a few weeks without treatment.

What is the preferred specimen for diagnosing C. felis?

Conjunctival swab.

Which stain can reveal C. felis intracytoplasmic inclusions?

Giemsa stain.

What laboratory techniques can be used to detect C. felis?

Cell culture or embryonated egg isolation

ELISA (detects family-specific LPS antigen)

PCR (conventional & real-time)

Serologic tests: Complement fixation, ELISA, Immunofluorescence

What is the antibiotic class of choice for feline chlamydiosis?

Tetracyclines.

Are vaccines available for C. felis?

Yes, both inactivated and live vaccines are available for parenteral use.

Do vaccines prevent C. felis infection and shedding?

No, vaccines reduce clinical signs but do not prevent infection or shedding.

Can C. felis infect humans?

Yes, but rare cases of human conjunctivitis have been reported.

What is Equine Recurrent Uveitis (ERU)?

A chronic, recurrent intraocular inflammatory disease in horses.

What is the reported prevalence of ERU in the US?

8-25% of horses.

Which breed is at increased risk of developing ERU?

Appaloosas and horses with MHC class I haplotype ELA-A9.

What is the estimated financial impact of ERU in the US?

$100-250 million per year.

What is the most common infectious cause of ERU in the US?

Leptospira interrogans serovar Pomona.

What is the most common infectious cause of ERU in Europe?

Leptospira kirschneri serovar Grippotyphosa.

What is the role of autoimmunity in ERU?

Autoimmune responses to ocular tissue components contribute significantly to the disease.

How does molecular mimicry play a role in ERU?

Antibodies against Leptospira proteins (LruA, LruB) cross-react with ocular proteins (α-crystallin B, vimentin, β-crystallin B2), leading to inflammation and protein dysfunction.

What is immune privilege, and how is it affected in ERU?

The eye is normally an immune-privileged site, but the presence of Leptospira-directed antibodies in eye fluids suggests a breakdown of immune privilege.

What are the diagnostic methods for Leptospira-associated ERU?

Culture

- Requires special media (P80, EMJH)

- Takes several weeks

Microscopic Agglutination Test (MAT)

- Gold standard

- Significant titer: ≥1:400 or four-fold rise in paired samples

PCR (targeting lipl32)

- Highly sensitive and specific

Other tests with lower sensitivity

- Immunohistochemistry (IHC), Fluorescent Antibody Test (FAT), Dark-field microscopy

What is the causative agent of inclusion conjunctivitis in guinea pigs?

Chlamydia caviae.

Which age group of guinea pigs is most predisposed to inclusion conjunctivitis?

Young guinea pigs, especially those 1-2 months old.

What other clinical signs may occur in guinea pigs with Chlamydia caviae infection?

Rhinitis, lower respiratory tract disease, and genital infections (e.g., salpingitis, cystitis in females, urethritis in males).

Can guinea pigs exhibit subclinical signs of Chlamydia caviae infection?

Yes, subclinical disease can occur.

What is the appearance of Leptospira spp.?

Motile, tightly coiled spiral organisms with hooked ends.

How do Leptospira spp. stain?

Leptospira spp. are Gram-negative but stain poorly, requiring darkfield or phase contrast microscopy.

How many serovars of Leptospira are there?

Over 250 serovars, with different hosts, geographic distributions, and pathogenicities.

Where do pathogenic strains of Leptospira persist in animals?

In the renal tubules or genital tract of infected animals.

Where can Leptospira survive in the environment?

In ponds, rivers, moist soil, and mud.

How is leptospirosis transmitted?

Transmission occurs through contact with urine of infected animals, entering through abraded skin or intact mucous membranes.

Is leptospirosis a zoonotic disease?

Yes, leptospirosis is a worldwide zoonosis caused by pathogenic Leptospira species.

Which animals carry Leptospira spp. asymptomatically?

Many wild and domestic animals carry Leptospira spp. asymptomatically, particularly in the renal tubules.

What is leptospiral uveitis?

A late complication of systemic Leptospira infection, causing inflammation of the uveal tract of the eye (iris, ciliary body, choroid).

Can leptospiral uveitis cause blindness?

Yes, it can lead to reversible or irreversible blindness in humans and horses.

When was human leptospiral uveitis first described?

It was described by Weil in 1886.

What type of uveitis is associated with Leptospira spp. in humans?

Acute, non-granulomatous pan-uveitis.

What is the prognosis for human leptospiral uveitis with timely treatment?

Good prognosis if treated timely.

Is recurrence common in human leptospiral uveitis?

Recurrence is rare, but it has been reported.

What percentage of uveitis cases in endemic regions like India is caused by Leptospira spp.?

Leptospira spp. accounts for ~10% of all uveitis and one-third of infectious uveitis cases in endemic regions like India.