Lepto, Salmonellosis, Malignant Catarrhal Fever Flashcards
is leptospirosis zoonotic
yes
worldwide
what type of bacteria is lepto
aerobic
gram negative
spirochete
what is the host adapted type of lepto to cattle in USA
L. borgpetersenii serovar Hardjo type hardjo-bovis (HB)
what is the host adapted type of lepto to cattle in UK
L. interrogans serovar Hardjo type hardjo-prajitno (HP)
what is the route of transmission of lepto
Shed in bodily fluids ex. urine, milk, vaginal discharge, semen
Penetrates mucus membranes (eye, mouth, nose, genital tract)
Persists in environment in moist conditions
Chronic carriers — often asymptomatic, intermittent shedding, often seronegative/low titres
what is the risk factors of lepto
Open vs closed herd (x2)
Bulls vs AI (x4)
Sheep co-graze with cattle (x6)
Cattle have access to waterways (x8)
Excretion in during grazing, decreases when house and fed silage (increased acidity of urine?)
what is the pathogenesis of lepto infection
Infection of non-immune animals
Bacteremia
Multiplication systemically, liver etc
Antibody from day 5
From day 7 limited to immunologically privileged sites:
- Brain
- Joints
- Kidney tubules from which shed into urine for 18 months
- Reproductive tract
- Seminal vesicles in bull
- Uterus, placenta and fetus in cow
- Multiplies in fetus
what are the reproductive clinical signs of lepto
Infertility
- Leptospires in uterus causing inflammation and embryo death
Low conception rates
Abortion
- 6-12 weeks after infection
- Usually last 3 months of gestation
- Tends to affect young cattle more frequently
- Live born calves weak and unviable
Stillbirths
Weak calves
Milk drop syndrome or ‘flabby bag’
what is milk drop syndrome or ‘flabby bag’ caused by lepto
Sudden onset fever and agalactia
All 4 quarters of udder soft and flabby producing quantities of yellow/orange secretion which may contain small clots
May affect 50% of cows at one time
Milk has high leukocyte count and therefore high SCC
what are the clinical signs of lepto in calves <2 months and >2 months
Often non-host adapted serovars
Calves under 2 months of age (nervous signs):
- Meningitis, anorexia, severe depression
- Opisthotonus, trismus, muscle tremors, paddling
- Pyrexia (40.5-41.5ºC)
Calves over 2 months of age:
- Anorexia and dullness
- Rarely pallor, petechiation, jaundice, hemoglobinuria
how is lepto diagnosed
Direct methods:
- Dark ground microscopy
- Culture and ID (difficult)
- PCR
- Immunofluorescence/peroxidase in tissue
Indirect methods:
- Serology ELISA
- Blood
- Milk
what occurs to antibodies in lepto infection
Antibody levels rise at first and may be associated with clinical signs
They then fall
Abortion can take place with low levels of antibody (up to 12 weeks after infection)
Antibody is present in the serum of carriers and vaccinated animals
how is lepto diagnosed on a herd basis
Serology:
- Rising titre in paired samples taken 14 days apart
- Individual samples with titres >1:100 indicates chronic or active infection
Abortion:
- Fetal serology
- Culture
Bulk milk ELISA now regularly used for surveillance
what are the aims in lepto treatment
To reduce the # of infected animals (pre-vacc?)
To minimize urinary status
To reduce spread of organism to other cattle and species including humans
how is lepto treated
Dihydrostreptomycin 25mg/kg (repeat after 7d)
- Off data sheep
- Problems with milk loss if a whole herd treatment
Other sensitive antibiotics:
- Amoxycillin (15mg/kg)
- Oxytetracycline (20mg/kg IM)
- Tilmicosin (10mg/kg SC)
- If the product is administered during the dry period or to pregnant animals, milk should not be used for human consumption until 36d after calving
how is lepto controlled
ID and removal of carrier animals
Vaccination
Test/treat/vaccinate replacements
Hygiene with special attention to water supply
how should vaccination be done in dairy herds against lepto
Close contact with workers
Raise replacements separately therefore heifers are naive
Complete vaccination course in heifers before breeding
Spring booster
how should vaccination be done in beef herds against lepto
Youngstock usually acquire some level of immunity
what are the 3 important types of salmonella
S. enterica Dublin
S. enterica Mbandaka
S. enterica Typhimurium
what is the most common isolated serovar of salmonella in british cattle
S dublin
what does S. enterica Mbandaka cause in adults
Diarrhea & malaise
Abortion
what is the main source of S. enterica Mbandaka in cattle
Infected feed origin
Mostly larger herds supplementing feed/housing all year
what does S. enterica Dublin mainly infect
calves
who does S dublin mostly affect
calves and adult cattle
does S dublin cause latent or persistent carriers
yes
what is S dublin associated with
abortion
how is salmonella transmitted
feco-oral route
how is salmonella transmitted cattle to cattle
Carrier status important — asymptomatic, may shed intermittently especially in times of stress
Carriers can shed millions of bacteria per day in feces
Neighbouring herds, marts, shows, bulls
how is salmonella transmitted through slurry
persists for months and in soil for a year
how is salmonella transmitted through feed/water
watercourses and feedstuffs can be contaminated by other stock and wildlife
what is the prevalence of salmonella
No routine monitoring
- No one knows the scale of exposure
- Rely on laboratory diagnosis from clinical cases
- Requires material to be submitted
Under diagnosed
- 75% dairy
- 12% beef
- 4% calf reares
what are the risk factors for salmonella
Buying in cattle/co-grazing
High stocking density, group pens
Poor hygiene
Concurrent disease — fluke, BVDV?
Season
Age/stage — calves under 3 months, cattle in first 2 weeks of lactation
what are the clincal signs of salmonella and what do they depend on
range of clinical signs
- Acute or chronic enteritis
- Abortion
- Septicemia
- Reduced productivity
- Poor calf health
may be overlooked/underdiagnosed
severity may depend on infective dose and age/stage
what are the signs of acute enteritis caused by salmonella in calves
>2 weeks and adults
High fever, severe diarrhea, sometimes bloody, anorexia, colic, abortion
Severe dehydration
what is the mortality of acute enteritis caused by salmonella
up to 75%
what are the clinical signs of chronic enteritis due to salmonella
May follow acute enteritis
Reduced weight gain, intermittent diarrhea, inappetence
what can trigger clinical signs of chronic enteritis due to salmonella
Poor nutrition
Long transport times
Calving
Mixing
Crowding
when is septicemia commonly seen due to salmonella
Mainly seen in neonatal calves (<2-3 weeks)
what are the signs of septicemia due to salmonella
Depression, fever, lethargy, laboured breathing, nervous signs, rapid death (6-48hrs)
Dry gangrene of extremities after initial phase
Joint infections
when is abortion commonly seen due to salmonella
Usually 5-8 months of pregnancy
what are the clinical signs of abortion due to salmonella
+/- fever and anorexia
retained placenta and reduced lactation
can salmonella cause abortion storms
up to 25% of herd
what can salmonella also cause in calves
Pneumonia
Poor growth rates
Ill thrift
Meningitis
how is salmonellosis diagnosed on an individual basis
fecal culture
PM
serology
how is salmonella on an individual clinical case diagnosed using fecal culture
Fecal sample not swab
Pooling decreases sensitivity
Remember previous use of antibiotics will affect culture
how is salmonella on an individual clinical case diagnosed on PM
Culture a range of tissues
In abortions, culture fetal stomach contents
how is salmonella on an individual clinical case diagnosed using serology
Best results in calves 3-10 months
Poor seroconversion <12 weeks old
Cross reactivity
Retrospective due to time taken to seroconvert
how is salmonella diagnosed on a herd level
carrier animals
culture
serology
how are salmonella carrier animals diagnosed
shedding may be intermittent
3 serology tests over 8 months
how can salmonella be diagnosed on a herd level using culture
slurry samples or feces of cases
how can salmonella be diagnosed on a herd level using serology
Bulk milk tank
- Good for continued monitoring (dairy)
Serology of all animals
Serology of a subset of animals
- Calves
- Those showing clinical signs
- 10 youngest calves over 12 weeks
how is salmonella treated
Early treatment is essential for septicemia salmonellosis
- S dublin usually susceptible to antibiotics
Controversy regarding the use of antimicrobials for intestinal salmonellosis
- Carrier status
Intestinal cases may cure clinical but not bacteriology
how is salmonella controlled
In a negative herd:
- Prevent entry using biosecurity
If already infected:
- Biocontainment (and biosecurity)
how is salmonella controlled using biosecurity
Maintain a closed herd or source new stock from high health status farms
Quarantine all in-coming stock for at least 4 weeks
Avoid shared equipment, bulls and grazing areas
Maintain good fences
Protect feed and bedding from vermin
Use mains water (not natural source)
Provide farm clothing for visitors or clean and disinfect boots/clothing before entering/leaving
Investigate abortions, scour cases or other illness as early as possible
Consider herd vaccination with Bovivac S (MSD)
how is salmonella controlled using biocontainment
egregate and treat clinical cases
All buildings should have good drainage and waste removal
Clean and disinfect calving/maternity pens and buildings between occupancies
Remove calf from dam ASAP
Colostrum management
Do not feed milk from ill cows to calves
Only spread slurry on arable land
Strict personal hygiene
Zoonotic risk
- Esp older people and children
- Do not consume unpasteurized milk
how is salmonella controlled using vaccines
bovivac S
the only licenced for bovine salmonellosis
contains both S typhimurium and S dublin
inactivated vaccine
what is the causative agent of malignant catarrhal fever (MCF) in wildebeest
Causative agent of wildebeest-associated MCF (WA-MCF) is Alcelaphine HV-1 (AHV-1)
what is the causative agent of malignant catarrhal fever (MCF) in sheep
Causative agent of sheep-associated MCF (SA-MCF) is ovine herpesvirus 2 (OvHV-1)
who are the natural and dead end hosts of MCF
sheep and wildebeest are natural hosts
cattle, deer and pigs are dead end hosts
how is MCF transmitted
Direct:
Aerosol
May be intermediate host (? flies)
Evidence for distance transmission
Windborne/mechanical?
how do cases of MCF typically arise
Typically sporadic, multiple cases usually caused by close proximity of lambing ewes to housed cattle
Reactivation during calving/lambing
what are the clinical signs of MCF
‘head and eye’ peracute, intestinal
Extreme dullness
Anorexia
Agalactia
Copious mucopurulent oculo-nasal discharge +/- blood
Drooling of saliva (‘ropes’)
Dyspnea and stertorous breathing
Loss of condition
Usually fatal
Survive ~1 week
Pyrexia (41ºC)
Congestion of scleral vessels, centripetal corneal edema, hypopyon
Corneal neovascularization
Diffuse oral ulceration with pain (loss of tips of oral papillae at commissures of lips) extending onto the rhinarium
Generalized lymphadenopathy + lymphocytosis
Dermatitis
- Sweating, crusting lesions
- Severe ulcerated lesions on the teats
Cystitis +/- pyuria
Altered fecal consistency
(sloughing of horns and horn of the digits)
what is the pathology of MCF
Lesions in virtually every system
Hydropic degeneration
Vesicle formation and erosion in stratified squamous epithelium
Ulcers coalesce and can become very extensive
Vasculitis:
- Perivascular cuffing with lymphoid cells
Paracortical expansion in lymphoid tissues
how is MCF diagnosed
Antibodies in serum or from affected tissues
- PCR for virus
- Tissue
- Whole blood
Exclude important ddx
- Mucosal disease
- FMD
- Bluetongue
how is MCF treated
euthanasia
how is MCF controlled
avoid contact with sheep esp during lambing
