Infectious Diseases of Ruminants Flashcards
(114 cards)
1
Q
What is the gestation of a sheep?
A
147 days
2
Q
What is an acceptable level of abortion in the sheep herd
A
less than 2 %
3
Q
Name the most common reproductive pathogens in sheep
A
Chlamydia abortus - enzootic abortion Toxoplasma gondii Salmonella abortus ovis Campylobacter fetus fetus border disease Schmallenburg
4
Q
What steps can be taken to help control reproductive pathogens?
A
Vaccination - in some cases
isolate infected ewes
remove contaminated material - abortion material
test new stock or have a closed herd
5
Q
What reproductive pathogens is there a vaccine for?
A
chlamydia
Toxoplasma
Schmallenburg
6
Q
Describe the general features of chlamydia abortus
A
- zoonotic
- gram -v cocci
- common in indoor systems
- carrier ewes can shed in oestrus
- can survive for several days in the environment
- strong immunity develops after infection
- ewes rarely ill with this pathogen
- 2 phases - intracellular reproductive stage and the extracellular infectious phase
- good at evading the immune system as replicate in tropholastic cells in repro tract
- infect the placenta cause necrosis and thickening resulting in a leathery appearance
7
Q
What is the treatment and control for chlamydia abortus
A
live attenuated vaccine provides strong durable immunity, given 4 weeks before tupping
Treat all ewes yet to lab with a course of long acting oxytetracycline - repeat in 2 weeks
8
Q
What are the consequences of chlamydia abortus infection at different stages of pregnancy?
A
- 0-90 days = reabsorption
- 90 + days = abortion
- non-pregnant = bacteria colonise reproductive tract and infect the next time the ewe is pregnant
- lamb born = may be infected and abort their first lamb
9
Q
Describe the general features of toxoplasma gondii
A
- zoonotic
- protozoa
- cats are the definitive host - shed oocysts in faeces
- have a wildlife reservoir
- picked up orally via oocyst ingestion
- strong immunity once exposed
- frosted strawberry cotyledons on placenta
10
Q
how do you control treat toxoplasma gondii
A
toxovac - liva attenuated vaccine given 3 weeks before tupping
control rodent and cat population and ensure feed store and water aren’t contaminatable
11
Q
Describe salmonella abortus ovis
A
- zoonotic
- gram -ve
- present in healthy carriers
- infected ewes become ill with metritis
- causes abortion
12
Q
Describe the control and treatment of salmonella abortus ovis
A
- treat those infected with NSAIDs and long acting oxytetracycline and the rest of the group with long acting oxytetracycline, repeat in 7-10 days
No vaccine available
13
Q
Describe Campylobacter fetus fetus and it’s treatment
A
- zoonotic
- causes abortion in the last 6 weeks of pregnancy
- ewes become ill with metritis
- carrier sheep shed bacteria in discharge
- treat infected ewes with broad spectrum antibiotics
14
Q
Describe Listeria Monocytogenes and it’s treatment
A
- often due to poor or contaminated silage
- causes encephalitis, abortion and septicaemia 1-2 weeks after eating the silage
- soil born gram positive pathogen
- treat with penicillin or oxytetracycline
15
Q
Describe tick-borne fever and it’s treatment
A
more common in upland areas
caused by anaplasma phagoctophilla - an immune suppressant
treat with pyrethroid before turning out to top tick infestation
16
Q
Describe Border disease virus
A
- pestivirus
- no clinical signs in non-pregnant ewes
- results in abortion or hairy shaker lambs (cerebral hypoplasia, hypermetra and ataxia)
17
Q
Coxiella burnetti - Q fever
A
- zoonotic
- environmentally resistant
- gram -ve bacteria
- spread via inhalation or direct contact
- if non-pregnant the infection remains latent and causes abortion the following year
18
Q
Describe Schmallenburg
A
- orthobunya virus transmitted by cullecoides midge
- mild/no illness in non-pregnant animals
- causes abortion, still birth or deformed lambs
19
Q
What is mastitis?
A
Inflammation of the mammary gland
20
Q
What are the two presentations of mastitis?
A
clinical = milk changes, udder changes, system changes
Sub-clinical = no visible clinical signs but do find changes in milk quality, quantity and an increased somatic cell count
21
Q
why is mastitis important ?
A
results in significant economic loss
Is a significant welfare issue
22
Q
How is mastits graded?
A
1 - sub-clinical, mild signs - milk changes
2A - acute - changes in milk, hot painful udder
2C - chronic - changes in milk and hard lumpy udder
3 - changes in milk, systemic illness, inflamed necrosed udder
23
Q
What are the consequences of mastitis?
A
- cow may clear up infection itself
- cow may be unable to clear infection and develop chronically persistent bacterial infections
- can result in permanent udder damage and decreased milk yield
- death due to chronic infection or involuntary cull
24
Q
Immune function in the cow depends on…
A
genetics nutrition stress husbandry - esp environment vaccinations stage of lactation
25
What is the most common point of entry for mastitis pathogens
through teat opening - can be due to damage, bad genetics or post milking - teat can take up to 20 mins to seal
26
What are the two types of mastitis pathogen?
environmental
| contagious - obligate pathogens
27
How are mastitis pathogens identified?
- culture and sensitivity - can't give antibiotics for at least before taking sample
- PCR - detects bacterial DNA so can give antibiotics as will still detect dead material but limited to a few common pathogens
28
Give examples of some common pathogen associations
- chronically increased SCC in individuals / herd = gram +ve
- spike in SCC with quick recovery = gram -ve
- low SCC but lots of clinical mastitis = gram -ve
- SCC or clinical mastitis in the first month post calving = infection likely to have been picked up in the dry period
29
What are common places mastitis bacteria can be picked up from
- teat skin
- udder
- fomites - milking equipment
- flies
- tonsils
- vagina
- people - milkers hands
30
Name the environmental causes of mastitis
```
E.coli
Strep uberis
Klebsiella
Yeasts
Pseudomonas
Bacillus Careus and Bacillus licheniformis
```
31
Name the contagious causes of mastitis
```
Staph aureus
Strep agalactiae
Coagulase negative Staphs
Mycoplasma bovis
Strep dysgalactiae
```
32
Describe Staphylococcus Aureus
- Gram +ve cocci
- Alpha toxin producing
- contagious pathogen
- persists intracellularly in the udder making the infection difficult to clear, protein A prevents immune detection
- phagocytosis is inhibited by it's pseudocapsule
- contains beta-lactimase so is resistant to penicillins
- manifests in secretory tissue - can cause abscesses which damage milk ducts
- often responsble or recurring chronic infection
- all grades common - sub-clinical infections with high SCC seen regularly
- Grade 3 is seen commonly in newly calved cows - causing toxaemia, necrosis and gangrene of the udder
- phagocytosis is inhibited by it's pseudocapsule
- contains beta-lactimase so is resistant to penicillins
33
How do you treat Staph Aureus infection
- antibiotic response poor
- teat amputation
- fluids and NSAIDs
- strip out with oxytocin and dry off
- antibiotics - tylosin systemically
cloxacillin locally
- if severe, cull
34
Describe Strep Agalactiae including treatment
- gram +ve cocci
- contagious pathogen
- non-haemolytic
- the udder and teat act as infection reservoirs
- often sub-clinical or mild symptoms, systemic illness rare
- not associated with persistent infection
- easily eliminated by beta lactam antibiotics
35
Describe coagulase negative staph species including treatment
- minor pathogen
- contagious
- causes mild disease and increased SCCs
- often clears spontaneously
- responds well to antbiotics
36
Describe Strep Dysgalactiae including treatment
- Gram +ve cocci
- contagious pathogen
- part of the summer mastitis complex
- responds well to penicillin
- can cause persistent infections
37
Describe Mycoplasma Bovis
- gram -ve
- less common
- contagious pathogen
- can also cause infertility, keratoconjunctivitis, pneumonia, metritis and arthritis
- causes a marked drop in milk yield and a swollen quarter but cows are rarely systemically ill
- aerosol spread, highly contagious
- poor response to antibiotics won't respond to beta lactams due to lack of cell wall
- dump milk fed to calves can cause pneumonia
- difficult to culture - requires a special medium
- clinical infection results in ulceration and abscessation and destruction of the infected quarter
- subclinical infection results in increased SCCs and low milk yields
38
Describe Klebsiella
- gram -ve
- environmental pathogen
- commonly found in sawdust or dirty parlous water
- causes acute mastitis similar to that of E.coli
39
Describe Yeasts
- associated with wet mouldy bedding
- also from poor hygiene in the milking parlour
- environmental pathogen
40
Describe Pseudomonas
- gram -ve
- associated with sawdust bedding and poor hygiene
- often acute and difficult to treat
- environmental pathogen
41
Describe Bacillus Careus and Bacillus licheniformis
- gram +ve
- cause of acute mastitis
- environmental pathogens
42
Describe E.coli
- gram -ve rod
- environmental pathogen
- commonly seen with poor housing conditions and straw bedding
- clinical cases often seen in early lactation, often acquired in the dry period
- rapidly proliferates in the udder releasing LPS endotoxins which damage vascular and secretory tissue
- endotoxaemia at risk of developing
- can produce all grades of mastitis
- Grade 3 is most common and results in a very sick cow, often post calving
43
Describe the treatment for E.coli
- With grade 3, strip out udder using oxytocin
- give systemic and local anibiotics, fluid therapy and NSAIDs
- vaccine available to reduce severity of the mastitis (given in 3 doses - 45 and 10 days pre-calving and 7-8 weeks post calving
44
How is mastitis generally controlled?
- milk affected cows last to reduce spread
- maintain good hygiene
- fly spray before turning out
- trip out and teat seal before dry period
- good breeding
- sand bedding rather than straw - has less bacterial growth
- don't feed dump milk to calves
45
Describe Strep Uberis
- gram +ve cocci
- non-haemolytic
- environmental pathogen
- main source is faeces
- survives well in bedding
- can be contagious - cow adapted strains in the tonsils, genital ang GI tracts
- can cause all grades of mastitis
- persistent subclinical infection common
- have the ability to hide in the mammary epithelium to avoid immune detection
- hyaluronic acid capsule prevents neutrophil and antibody attachment
- cull chronic cases
- infection common in early lactation
- requires long course of an antibiotic which acts intracellularly e.g. penicillin
46
What is summer mastitis ?
- affects any outdoor cattle
- spread by flies
- results is a hot, swollen, painful udder often with thick purulent discharge
- cow can also be lame and systemically ill
- response to antibiotics is poor
- affected quarter often irreparable
- remove infected animal to prevent spread
- strip quarter 3x daily and give systemic antibiotics - sometimes cutting the teat to allow drainage is advised
47
What are the clinical signs of Jhones disease
- weight loss
- bubbly diarrhoea
- oedema - bottle jaw
- remains bright and eating
- cattle not showing clinical signs have reduced milk yield, increased likelihood of contracting mastitis, lameness, respiratory and GI problems
48
How is Jhones transmitted
- excreted in faeces,
- only a low dose required to be infective
- calves most commonly affected in first 8 weeks of life
- Faeco-oral transmission most common
- calves can also be infected via milk or colostrum from infected mother or cows
- a small number are exposed in utero
- uncommon to acquire as adults
49
Describe the general faetures of Jhones
- zoonotic link to chrones in people
- affects domestic and wild ruminants and rabbits
- clinical disease seen in animals over 3
- clinical presentation linked to stress - often post calving
50
Describe the Jhones bacterium
- mycobacterium avium paratuberculosis (MAP)
- GRAM +VE
- slow growing
- acid fast anaerobe
- weak host specificity
- can survive years in the environment
51
What is the pathology of Jhones
- causes diffuse thickening of the gut
- infects macrophages in payers patches in the gut then spreads to GI lymph nodes
- results in complete loss of immune control
52
Control of Jhones
- no quick fix
- focus on preventing calf infection
- test new stock
- feed milk replacer rather than dump milk
- don't feed pooled milk or colostrum
- remove calf from mother ASAP
- ensure calves are fed from confirmed negative cows
- blanket test stock and cull or manage those affected
- avoid calf contact with adult faeces
53
How is MAP tested for?
- faecal culture - gold standard - detects shedders
- ELISA - detects animals struggling with infection who are likely to be shedding but poor for detecting infectious individuals
- the antibody response can wax and wane so ELISA tests aren't always reliable
- antibody positive animals are likely to be shedding - -
- PCR - likely to be used increasingly as specificity and sensitivity is increasing
54
What is the immunology behind Jhones
- cell mediated immune response is initially protective and stops disease progression
- when the cow is under stress or immune challenge, TH2 immunity takes over and suppresses cell mediated immunity allowing proliferation and progression of disease
55
Describe the transmission of neonatal calf diarrhoea pathogens
- faeco-oral transmission is the main route
- additionally fomites and environmental contamination play a role
- adults shed in low numbers
- older calves pass the pathogens to the younger naive ones
- some calves act as asymptomatic carriers
56
what are the Factors affecting the incidence of neonatal calf diarrhoea
- colostrum intake
- calf's immune status
- inadequate nutrition
- environment - hygiene level
- stressors - often linked to animal management
- pathogens present - viruses, bacteria, protozoa, parasitic
57
Name the main pathogens involved in neonatal calf diarrhoea
```
rotavirus
coronavirus
bovine calicivirus
bredavirus
astrovirus
cryptosporidium
E.coli
Salmonella
```
58
Which pathogens commonly infect older calves
- cryptosporidium
- coronavirus
- rotavirus
59
Which pathogen commonly affects calves up to 6 days old?
E.coli
60
How do viruses and cryptosporidium cause diarrhoea
due to vilus damage resulting in malabsorption drawing water into the gut
61
How does E.coli and Cholera cause diarrhoea
Due to hypersecretion due to enterotoxin release
62
How can you identify the cause of neonatal calf diarrhoea
- bacterial culture from faeces
- immunofluorescent antibody test
- ELISA antigen test
- histopathology
- microscopic analysis of the faeces
- serotyping
63
How should neonatal calf diarrhoea be treated
no need for antibiotics supportive fluid therapy, oral rehydration and TLC should be sufficient
64
How can malabsorpion lead to metabolic acidosis
results in a reduction in lactase activity resulting in more undigested food in the colon which is then subject to fermentation. The increased fermentation results in osmotic diarrhoea and acid production
65
Describe the key features of salmonella in neonatal calf diarrhoea
salmonella dublin is species specific to cows, the other common isolate is salmonella typhimurium which has serious zoonotic implications
- it is a gram -ve rod shaped bacterium
66
what colour stain do gram positive's turn?
purple
67
what colour stain do gram negative's turn?
pink
68
Describe the key features of rotavirus in neonatal calf diarrhoea
- double stranded DNA virus with a wheel like appearance
| - infects cells via a group A surface antigen
69
Describe the key features of coronavirus in neonatal calf diarrhoea
single stranded RNA virus
causes enteritis and scour in calves and winter dysentery in adults
Can also cause respiratory disease
70
Describe the key features of bovine calicivirus in neonatal calf diarrhoea
single stranded RNA virus
71
Describe the key features of bredavirus in neonatal calf diarrhoea
RNA virus
| has zoonotic potential
72
Describe the key features of astrovirus in neonatal calf diarrhoea
unclassified RNA virus
| widespread antibodies to the virus isolated from cattle
73
Describe the key features of cryptosporidium in neonatal calf diarrhoea
2 main causative agents - cryptosporidium parvum and enteric coccidia
non-host specific - zoonotic
infected animals secrete oocysts which are immediately infective and environmentally resistant
carrier animals exist
74
Describe the key features of E.coli in neonatal calf diarrhoea
- gram -ve rod
- many subtypes exist some are commensal
- minor gut pathogen in calves
- enterotoxic e.coli causes diarrhoea in calves under 6 days old
- causes rapid dehydration and death if not treated within 24-48 hours of onset
- bacteria uses pili to adhere to enterocytes and produces enterotoxin which causes a host inflammatory response
- a rise in c-AMP inhibits sodium absorption from the gut by enterocytes which stimulates secretion into the gut lumen causing an electrolyte balance. The same occurs with water and chloride ions
75
What is the importance of reproductive pathogens in cattle
- has a financial impact
- lower number of viable offspring
- cost of treatment
- increased involuntary culling
- increased calving intervals
76
Name pathogens associated with reproductive infections e.g. vaginitis and endometritis
- E.coli
- Fusobacterium necrophorum
- Trueperella pypgenes
- bovine herpes virus 1 and 2
- campylobacter
77
What is vaginitis/cervicitis
inflammation of the cervix and vagina, common after injury due to dystocia
results in purulent vaginal discharge
often due to a mixed bacterial infection
78
what is clinical endometritis
inflammation of the endometrium with purulent uterine disharge
79
What is subclinical endometritis
inflammation of the endometrium minus any purulent discharge but on cytology see lots of polymorphonuclear neutrophils
80
Name pathogens associated with abortion in a cow
- bacterial brucellosis - notifiable but uncommon
- infectious bovine rhinotracheitis - herpes virus 1
- lysteria monocytogenes
- salmonella
- bacillus licheniformis
- brucella abortus
- bovine viral diarrhoea virus
- campylobacter fetus venerealis
81
Describe the features of E.coli with regards to reproductive pathogenicity in cattle
- gram -ve
- prevalent during the first week post calving
- pathogenic to the uterus
- releases endotoxins
- often leads the way for trueperella pyogenes
82
Describe the features of Fusobacterium necrophorum with regards to reproductive pathogenicity in cattle
- gram -ve anaerobe
- opportunistic pathogen
- thrives in necrotic disease conditions
- pathogenicity relates to adhesion factors
- releases a toxin which affects leucocytes, macrophages and epithelial cells
- usually found post-partum
83
Describe the features of Trueperella pyogenes with regards to reproductive pathogenicity in cattle
- gram +ve
- opportunistic pathogen
- PLO toxin released - cholesterol dependent
- epithelial cells have protective devices against PLO
- bacteria has adhesion factors which allow binding to endometrial cells
- often found post-partum
84
Describe the features of Bovine herpes virus with regards to reproductive pathogenicity in cattle
- enveloped DNA virus
- causes pathological change in the endometrial cells
- passed on by bulls when breeding
85
What is a pyometra
- intrauterine accumulation of pus
- affected animals show no signs of heat
- often due to a mixed bacterial infection
86
Describe the features of Campylobacter with regards to reproductive pathogenicity in cattle
- gram -ve rods
- most common type - campylobacter fetus venerealis
- STD found in the cow's reproductive tract and the bull's prepuce
- common in natural service
- causes chronic endometritis, fetal death and abortion
- bulls should be regularly tested
87
Describe the features of Infectious bovine rhinotracheitis with regards to reproductive pathogenicity in cattle
- bovine herpes virus 1
- causes abortion
- have latent carriers - begin to shed when stressed
- intra-nasal vaccine available
88
Describe the features of Lysteria Monocytogenes with regards to reproductive pathogenicity in cattle
- associated with poor silage
- causes abortion and neurological signs
- gram +ve bacteria
89
Describe the features of Bovine Viral Diarrhoea with regards to reproductive pathogenicity in cattle
- pestivirus
- 5-7 day incubation
- 2 genotypes - type 1 causes mild to moderate disease while type 2, seen rarely in the UK causes severe diarrhoea with high mortailty
- causes abortion
- within the genotypes are two biotypes - a non-cytopathic type which rarely causes disease but crosses the foetal-materna barrier and a cytopathic type which is associated with mucosal disease in persistently infected animals
90
Describe the features of Salmonella with regards to reproductive pathogenicity in cattle
- zoonotic
| - salmonella Dublin most commonly associated with abortion
91
Describe the features of Bacillus licheniformis with regards to reproductive pathogenicity in cattle
gram +ve saprophyte
| causes abortion via necrotising placentitis
92
Describe the features of Brucella abortis with regards to reproductive pathogenicity in cattle
- no longer present in the UK
- intracellular pathogen
- animals remain infected for life
- abortion due to purulent placentitis and necrosis of the cotyledons
93
Briefly describe the general features of foot and mouth
- apthovirus
- highly infectious
- affects cloven hooved animals
- high morbidity, low mortality
clinical signs:
- fever
- lameness
- lesions in the oral cavity and on the feet, snout and teats
94
Briefly describe the general features of bovine digital dermatitis
- causes infectious lameness
- endemic
- very painful - welfare issues
- significant economic loss
- lesions located above the coronet between the heel - mainly seen on rear feet, more common in dairy cattle
- antibiotics lead to transient improvement
- presice cause unknown - campylobacter, mycoplasma, spirochates (found most frequencies), dichelobacter
- no effective treatment
- footbaths and topical teramycin +/- systemic penicillin or macrolides
- outbreaks in winter with housed cattle
- lots of reservoirs for infection
95
Briefly describe the general features of contagious ovine digital dermatitis
- pathology similar to bovine digital dermatitis- spirochaetes isolated
- visual diagnosis
- causes significant pain and suffering resulting in complete loss of the horn capsule
- no single effective treatment - footbaths, antibiotics - topical and systemic
- living near cattle is a risk factor
96
Briefly describe the general features of ovine foot rot
- extremely painful - causes rapid weight loss
- causes lameness and loss of body condition, can cause death by starvation and thirst
- begins as interdigital dermatitis which then leads to interdigital hoof wall lesions leading to separation of the hoof wall
- primary infectious agent dichelobacter nodosus a rod shaped gram-ve anaerobe
- produces extracellular proteases
- the infected foot is a reservoir for infection
- transmitted by direct and indirect contact
- may be polymicrobial
- treat with foot trimming, topical disinfectants and antibiotics, foot baths and occaisionally systemic antibiotics
97
Briefly describe the general features of ovine interdigital dermatitis (scald)
- most common lameness in sheep
- painful
- occurs in wet conditions
- considered an early indication of foot rot
- no foul smell
- red/pink inflammation between the two claws with white/grey scum on top
- same treatment as foot rot
98
Briefly describe the general features of bovine footrot
- sudden acute onset
- thought that an injury to interdigital skin is required for infection to take place
- results in severe lameness- animal seen non-weight bearing with a fever, milk yield decrease, anorexia and interdigital space swelling
- environment acts as an infection reservoir
- fusobacterium necrophorum and bacterioides melaninogenicus
99
What are the consequences of cattle lameness
- extremely painful - can result in hyper- algesia
- high yielders more susceptible
- lameness has an impact on milk yield
- has an impact on cyclicity an calving intervals
- increased involuntary culling
- decreases body condition score
- cost of treatment
100
What are the main viruses causing respiratory disease in cattle
- Bovine viral diarrhoea
- bovine herpes virus 1
- parainfluenza virus 3
- bovine respiratory syncitial virus
101
Describe the general features of bovine respiratory syncitial virus
- pneumovirus
- G protein needed to attach to cell
- RNA Virus
- Sheep and goats can also be affected
- Occurs predominantly in young animals
- Affects both beef and dairy cattle
- No passively derived immunity prevention but does reduce severity
- Targets lower respiratory tract
- Predisposes respiratory tract to secondary infection
- Fairly high morbidity
- Lab diagnosis required - virus difficult to identify - immuno assay commonly used or serum samples
- Treat with antimicrobial therapy to treat secondary infections and supportive fluid therapy. - - Most cases will recover within a few days without treatment
- Are vaccines available but efficacy questionable
102
Describe the clinical signs of bovine respiratory syncitial virus
```
Clinical signs:
Fever
Depression
Decreased food intake
Increased resp rate
Nasal and lacrimal discharge
Coughing
Secondary bacterial pneumonia
Interstitial emphysema
Histologically: see the formation of giant cells often containing eosinophilic inclusion bodies
```
103
Bovine Parainfluenza Virus 3
- Paramyxovirus
- RNA virus
- Common cause of infection in cattle - commonly mild infections
- Can give way to secondary infections
- Causes bronchitis, broncholitis and alveolar cell thickening and hyperplasia
-Clinical signs:
- pyrexia
- increased respiratory rate
- increased breathing sounds
- serous lacrimal and nasal discharge
- coughing
- Bacterial pneumonia is a common secondary infection
- Can see intracytoplasmic inclusion bodies in the lungs at 5-7 days, marked congestion and haemorrhage
- Treat secondary infections with antimicrobials along with NSAIDs and fluid therapy
Vaccines are available for IM or intranasal administration
104
Briefly describe infectious bovine rhinotracheitis
Herpes virus
Enveloped DNA virus
2-6 day incubation period
Commonly seen in cattle between 6-18 months old
Virus causes sloughing of epithelial cells in upper respiratory tract
Leaves animal open to bacterial infection "shipping fever"
Host restricted Neurotropic - can attack nervous system
Clinical signs:
- Inflamed nares
- conjunctivitis with lacrimal discharge
- fever
- anorexia
- coughing
Excess salivation
- disharge which progresses from serous to mucopurulent
- pitychial haemorrhage may be seen in respiratory tract mucosa
- sometimes focal areas of mucosal necrosis
105
briefly describe bovine viral diarrhoea virus
- Pestivirus
- 2 genotypes - BVDV 1 destroys alveolar macrophages and depletes lymphoid tissue
- Can infect calf in-utero - if infected in the first trimester the calf is aborted, if in the second the calf can become persistently infected but by the third trimester the calf is strong enough to fight it off
- Immunosuppression allows secondary bacterial respiratory infections
- Inactivated vaccine available contaning both virus genotypes
106
What is the causative agent of TB?
Mycobacterium Avium, Tuberculosis and Bovis are the most common causative agents
107
Describe the general features of the bovine strain of TB
Has a varied host range, is heat sensitive, is aerobic and is heat sensitive and will be killed by household bleach. Only a low infectious dose is required and it is spread via inhalation or ingestion.
90% of lesions occur in the caudal lung lobes and the bacteria spreads within the host via lymphatic channels. The bacteria enter macrophages where they reproduce and form lesions in the lungs where the bacteria proliferate.
108
What are the clinical signs of TB in cattle?
Progressive emaciation, chronic cogh, loss of appetite, fluctuating pyrexia, mastitis, pleuropneumonia, lung absesses, pericarditis
109
What gross lesions are seen with TB?
The bacteria form tubercles – small white nodules in the lymph nodes or organs
110
What measures are in place to control TB?
Cattle surveillance, enhanced biosecurity and husbandry practices, try to avoid / limit contact with badgers, closed herds, routine testing ( a reactor is more than 5mm swelling difference from the initial test), movement tracking
111
What type of virus causes foot and mouth?
Apthovirus affecting domestic and wild cloven footed animals
112
What are the clinical signs of foot and mouth?
Fever, lameness, oral lesions, snout lesions, teat lesions, drooling, depression lesions on the feet, abortion
113
How is foot and mouth transmitted?
Spread in milk, semen, by people and fomites, has airborne spread, can be passed on via direct contact. Can be picked up rally or by inhalation
114
What method of control are in place for foot and mouth?
Slaughter all infected and those exposed to infected animals, movement restrictions, vaccination, regular veterinary checks
