evaluating different pathogens

Question 1

what are the key mechanisms of immune evasion used by pathogens

Answer 1

Decoys:
- Virokines/viroceptors → viral proteins mimic host cytokines/receptors, disrupting signalling.
- Bacterial capsules → shield against phagocytosis.

Latency: viruses like herpes can “hide” by remaining dormant inside cells.

Immunoprivileged sites: infection in tissues less accessible to immune cells (e.g. CNS, eye).

Antigenic variation:
- Antigenic drift → gradual mutations (influenza, HIV).
- Antigenic shift → reassortment between strains, major change (influenza pandemics).

Direct immune attack:
- Infect and kill immune cells (e.g. HIV infects CD4+ T cells).
- Downregulate MHC or other effector molecules.
- Manipulate apoptosis or signalling pathways to favour survival.

Transmission advantages: Some pathogens even change host behaviour (e.g. rabies → aggression).

Question 2

how does FIV affect the immune system

Answer 2

• retrovirus. T-lymphotropic
• targets CD4+ T cells via CD134 receptor leads to gradual decline of CD4+ cells
• causes an inverted CD4+:CD8+ ratio
• leads to immune deficiency and cats therefore cant fight off normally manageable infections

Question 3

what are the stages of FIV infection

Answer 3

1. acute stage = mild illness (fever, neutropenia, lymphadenopathy)
2. sub clinical stage = often long, asymptomatic but CD4+ count steadily declines
3. terminal stage = secondary/opportunistic infections, chronic, cat cant fight on own

Question 4

how do you manage FIV positive cats

Answer 4

• supportive treatment to manage secondary infections
• prevention of infection (think dental care, vaccines, parasite control)
• keep indoors to reduce exposure to pathogens and prevent transmission (mainly though fights)
• avoid raw diets, provide good nutrition

Question 5

how does FIV virus work

Answer 5

Question 6

what is a commensal organism

Answer 6

• do not invade, only harmful if other circumstances present
• may help control pathogens as compete for places to live

Question 7

where do we find commensal organisms in the female reproductive tract

Answer 7

• perineum
• vulva
• clitoris
• vestibule
• vagina
• cervix (unless covered with mucus)
• uterus (during oestrus when cervix open or when ejaculation occurs into the uterus)

in order of many to few

Question 8

where do we find commensal organisms in the male reproductive tract

Answer 8

• preputial skil
• preputial lining
• penis
• urethra
• rarely within accessory sex glands and not normally within the vas deferens or testes

Question 9

what diseases occur to the male reproductive tract as a result of pathogen exposure

Answer 9

• dermatitis to the preputial skin
• posthitis to the preputial lining
• balanitis to the penis
• urethritis to the urethra
• prostatitis to the prostate
• orchitis to the testis

Question 10

what diseases occur in the female reproductive tract due to exposure to pathogens

Answer 10

• dermatitis/vulitis to the perineum
• vaginitis/vestibulitis to the vagina
• cervicitis to the cervix
• edometritis/metritis/pyometra to the uterus
• placentitis/infection of the fetus
• salpingitis to the uterine tube (rare)
• oopohoritis to the ovary (rare)

Question 11

how are reproductive pathogens transmitted

Answer 11

• via semen or vaginal secretion (venereal)
• other (resp tract)

Question 12

discuss uterine contamination post partum

Answer 12

• most commonly these are commensal organisms (as associated damage to endometrium is present as placenta detaches
• as deeper layers of the uterus are exposed the commensal organisms can penetrate to the myometrium and so the condition is called metritis
• animals with metritis are often sick
• sometimes the condition improves and only a more superficial contamination persists. this is endometritis

Question 13

how does uterine contamination occur at mating

Answer 13

• commensal bacteria enter the uterus in the mare, sow and bitch at the time of mating
• bacteria rapidly cleared by immune response and uterine contractions

Question 14

name a pathogenic bacteria that causes endometritis in the mare

Answer 14

taylorella

Question 15

name a pathogenic bacteria that causes endometritis in the cow

Answer 15

bovine venereal campylobacterosis

Question 16

how do viruses enter the repro tract

Answer 16

• pathogens do not have to enter via the repro tract
• a common route is via the resp tract
• some pathogens have different varieties and may be transmitted via the resp and repro tract

Question 17

how does herpes virus affect the repro tract

Answer 17

• many transmitted by aerosol and replicate in the respiratory tract so there is commonly resp tract disease
• viruses spread to other organs and may lie dormant
• if the femal is preg the virus may invade the placenta and cause resorption or abortion
• if the female becomes pregnant the stress of pregnancy may allow viral recrudescence of the activated virus which invades placenta and results in preg loss

Question 18

equine herpes virus 1 causes disease to the repro tract via resp tract how

Answer 18

causes resp disease and placentitis leading to abortion

Question 19

canine herpes virus 1 is a respiratory virus causing

Answer 19

resp disease and placentitis leading to abortion

Question 20

feline herpes virus 1 is a resp tract disease and causes

Answer 20

may cause abortion but rare

Question 21

bovine herpes virus 1 is a resp virus and causes

Answer 21

IBR, can cause abortion

Question 22

equine herpes virus 3 causes

Answer 22

repro tract pathogen that causes vesicular lesions on the penis and vulva (coital exanthema)

Question 23

canine herpes virus 1 causes

Answer 23

repro tract pathogen that causes vesicular esions on the penis and vulva

Question 24

bovine herpes virus 1 causes

Answer 24

repro pathogen that causes vesicular lesions on the penis and vulva

Question 25

what routine screening is performed in horses for repro pathogens

Answer 25

stallions: penile swabs for bacterial venereal pathogens (taylorella, klebsiella, pseudomonas), EVA serology mares: clitoral swabs for bacterial venereal pathogens (as above) EVA serology