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Module 21: Ruminant Production > Lepto, Salmonellosis, Malignant Catarrhal Fever > Flashcards

Lepto, Salmonellosis, Malignant Catarrhal Fever Flashcards

1
Q

is leptospirosis zoonotic

A

yes

worldwide

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2
Q

what type of bacteria is lepto

A

aerobic

gram negative

spirochete

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3
Q

what is the host adapted type of lepto to cattle in USA

A

L. borgpetersenii serovar Hardjo type hardjo-bovis (HB)

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4
Q

what is the host adapted type of lepto to cattle in UK

A

L. interrogans serovar Hardjo type hardjo-prajitno (HP)

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5
Q

what is the route of transmission of lepto

A

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

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6
Q

what is the risk factors of lepto

A

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?)

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7
Q

what is the pathogenesis of lepto infection

A

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
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8
Q

what are the reproductive clinical signs of lepto

A

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’

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9
Q

what is milk drop syndrome or ‘flabby bag’ caused by lepto

A

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

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10
Q

what are the clinical signs of lepto in calves <2 months and >2 months

A

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
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11
Q

how is lepto diagnosed

A

Direct methods:

  • Dark ground microscopy
  • Culture and ID (difficult)
  • PCR
  • Immunofluorescence/peroxidase in tissue

Indirect methods:

  • Serology ELISA
  • Blood
  • Milk
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12
Q

what occurs to antibodies in lepto infection

A

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

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13
Q

how is lepto diagnosed on a herd basis

A

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

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14
Q

what are the aims in lepto treatment

A

To reduce the # of infected animals (pre-vacc?)

To minimize urinary status

To reduce spread of organism to other cattle and species including humans

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15
Q

how is lepto treated

A

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
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16
Q

how is lepto controlled

A

ID and removal of carrier animals

Vaccination

Test/treat/vaccinate replacements

Hygiene with special attention to water supply

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17
Q

how should vaccination be done in dairy herds against lepto

A

Close contact with workers

Raise replacements separately therefore heifers are naive

Complete vaccination course in heifers before breeding

Spring booster

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18
Q

how should vaccination be done in beef herds against lepto

A

Youngstock usually acquire some level of immunity

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19
Q

what are the 3 important types of salmonella

A

S. enterica Dublin

S. enterica Mbandaka

S. enterica Typhimurium

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20
Q

what is the most common isolated serovar of salmonella in british cattle

A

S dublin

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21
Q

what does S. enterica Mbandaka cause in adults

A

Diarrhea & malaise

Abortion

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22
Q

what is the main source of S. enterica Mbandaka in cattle

A

Infected feed origin

Mostly larger herds supplementing feed/housing all year

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23
Q

what does S. enterica Dublin mainly infect

A

calves

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24
Q

who does S dublin mostly affect

A

calves and adult cattle

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25
does S dublin cause latent or persistent carriers
yes
26
what is S dublin associated with
abortion
27
how is salmonella transmitted
feco-oral route
28
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
29
how is salmonella transmitted through slurry
persists for months and in soil for a year
30
how is salmonella transmitted through feed/water
watercourses and feedstuffs can be contaminated by other stock and wildlife
31
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
32
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
33
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
34
what are the signs of acute enteritis caused by salmonella in calves
\>2 weeks and adults ## Footnote High fever, severe diarrhea, sometimes bloody, anorexia, colic, abortion Severe dehydration
35
what is the mortality of acute enteritis caused by salmonella
up to 75%
36
what are the clinical signs of chronic enteritis due to salmonella
May follow acute enteritis Reduced weight gain, intermittent diarrhea, inappetence
37
what can trigger clinical signs of chronic enteritis due to salmonella
Poor nutrition Long transport times Calving Mixing Crowding
38
when is septicemia commonly seen due to salmonella
Mainly seen in neonatal calves (\<2-3 weeks)
39
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
40
when is abortion commonly seen due to salmonella
Usually 5-8 months of pregnancy
41
what are the clinical signs of abortion due to salmonella
+/- fever and anorexia retained placenta and reduced lactation
42
can salmonella cause abortion storms
up to 25% of herd
43
what can salmonella also cause in calves
Pneumonia Poor growth rates Ill thrift Meningitis
44
how is salmonellosis diagnosed on an individual basis
fecal culture PM serology
45
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
46
how is salmonella on an individual clinical case diagnosed on PM
Culture a range of tissues In abortions, culture fetal stomach contents
47
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
48
how is salmonella diagnosed on a herd level
carrier animals culture serology
49
how are salmonella carrier animals diagnosed
shedding may be intermittent 3 serology tests over 8 months
50
how can salmonella be diagnosed on a herd level using culture
slurry samples or feces of cases
51
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
52
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
53
how is salmonella controlled
In a negative herd: * Prevent entry using biosecurity If already infected: * Biocontainment (and biosecurity)
54
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)
55
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
56
how is salmonella controlled using vaccines
bovivac S the only licenced for bovine salmonellosis contains both S typhimurium and S dublin inactivated vaccine
57
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)
58
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)
59
who are the natural and dead end hosts of MCF
sheep and wildebeest are natural hosts cattle, deer and pigs are dead end hosts
60
how is MCF transmitted
Direct: Aerosol May be intermediate host (? flies) Evidence for distance transmission Windborne/mechanical?
61
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
62
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)
63
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
64
how is MCF diagnosed
Antibodies in serum or from affected tissues * PCR for virus * Tissue * Whole blood **Exclude important ddx** * Mucosal disease * FMD * Bluetongue
65
how is MCF treated
euthanasia
66
how is MCF controlled
avoid contact with sheep esp during lambing

Module 21: Ruminant Production (21 decks)

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