Food Animal Lymphoid Organ Enlargement

What are the THREE common causes of lymphadenopathy?

1. Abscess/cellulitis of area drained

2. Lymphosarcoma

3. Caseous lymphadenitis

What are the THREE uncommon causes of lymphadenopathy?

1. Tuberculosis

2. Malignant catarrhal fever

3. Hairy vetch toxicosis

What are the SIX major external lymph nodes palpable on physical exam?

1. Submandibular

2. Parotid

3. Retropharyngeal

4. Prescapular (superficial cervical)

5. Prefemoral (subiliac)

6. Supramammary (superficial inguinal)

What lymph node is often enlarged with mastitis or lameness?

Supramammary ln

What are the THREE major palpable internal lymph nodes on rectal?

1. Renal

2. Sublumbar (lumbar aortic)

3. Deep inguinal (iliofemoral)

True or False: Malignant lymphoma and lymphoma are the same as lymphosarcoma.

True!

What are the FOUR classifications of lymphosarcoma?

1. Calf (juvenile)

2. Thymic (adolescent)

3. Cutaneous

4. Adult (BLV-associated)

What is the only form of lymphosarcoma associated with BLV?

Adult (Enzootic)

Juvenile form is extremely (common/rare) and occurs mostly during the age of ————-, but can also be seen in younger or older patients.

Rare

3-6 months

Are beef or dairy cows predisposed to juvenile form?

Dairy

True or False: Juvenile form is often characterized by lymphadenopathy and poor-doers.

True!

What age and type of cow (beef vs dairy) are most common in the thymic form, which is also rare?

6-24 months

Beef

True or False: Thymic forms features generalized lymphadenopathy similar to juvenile form.

False! There is NOT generalized lymphadenopathy- tumors of thymus and REGIONAL lymph nodes

What are THREE major clinical signs associated with thymic form?

1. Local compression from tumor in neck/thorax

2. Dysphagia/bloat

3. Congestive heart failure (brisket edema, jugular distention)

True or False: Thymic form is invariably fatal.

True!

What form features multifocal cutaneous nodules that are grey-white with circular plaques that may regress and spontaneously recur?

Cutaneous form

What age range is most likely for cutaneous form?

Young adults (not age-specific like other two sporadic forms)

What are the FOUR major locations of cutaneous LSA?

1. Anus

2. Vulva

3. Shoulders

4. Flank

What would a biopsy of cutaneous LSA show?

Lymphocytic infiltrates

What is prognosis of cutaneous LSA?

Poor (internal AND external lymphadenopathy)

What is the most common neoplastic disease of cattle?

Adult lymphosarcoma (Enzootic bovine leukosis or malignant lymphoma)

What are the TWO biggest economical factors of adult lymphosarcoma?

1. Carcass condemnation (if systemic disease evident)

2. Export limitations

Match the subclass of retrovirus to the disease:

Lentivirus

Oncovirus

Spumavirus

Bovine syncytial virus

BIV

BLV

Oncovirus: BLV

Lentivirus: BIV

Spumavirus: Bovine syncytial

What makes retroviruses unique?

Reverse transcriptase (RNA -> DNA)

True or False: Once animals are infected with BLV, they are infected and seropositive for life, and it is difficult for the host to eliminate the virus.

True!

Is BLV more prominent in beef or dairy?

Is it a worldwide issue?

Dairy (40% positive opposed to 10%)

Yes

True or False: There is a higher BLV prevalence in smaller herds.

False! There is a higher BLV prevalence in LARGER herds.

True or False: BLV prevalence continues to increase over time and older age groups are affected at higher rates compared to younger (i.e. 15 months vs 1 month).

True!

What must occur for transmission of BLV?

Give at least THREE specific examples.

Spread of lymphocytes containing proviral DNA

1. Blood (dehorners, tattoo pliers, palp sleeves)

2. Nasal/saliva

3. Milk/colostrum

4. Semen

5. In utero

What are the THREE forms of BLV infection?

Which is the majority of BLV-infected cattle?

1. Asymptomatic

2. Persistent lymphocytosis

3. Lymphosarcoma

Asymptomatic

What form of BLV makes up 30% of positives and features increased lymphocyte counts?

Persistent lymphocytosis

What TWO ways can persistent lymphocytosis form of BLV be classified based upon lymphocyte counts?

1. >3 standard deviations on repeated blood counts for 3 months

2. >15,000 lymphocytes/ul on 2 blood samples 3 months apart

True or False: Persistent lymphocytosis is a malignant proliferation and is considered a precursor to lymphosarcoma.

False! Persistent lymphocytosis is a BENIGN proliferation and is NOT a precursor to lymphosarcoma.

What form of BLV makes up less than 5% of cattle and 1.7% of BLV-positives?

Are cattle younger or older than the cutaneous form?

Is it focal or multicentric?

Lymphosarcoma

Older (4-8 years)

Multicentric

What are the SIX major predilection sites of lymphosarcoma?

1. Lymph nodes (>90%)

2. Abomasum

3. Heart (right atrium)

4. Uterus

5. Spinal cord

6. Intestines

True or False: Lymphosarcoma can have non-specific signs (anorexia, decreased production, weight loss), lymphadenopathy (internal especially), and organ signs (melena, posterior paresis, right heart failure).

True!

True or False: Tibial paresis, dog sitting, and more can be caused by lymphosarcoma.

True!

True or False: Clin path finidngs are a good way to support your diagnosis.

False! Leukemia is not present consistently and lymph node aspirate is not reliable. Effusion cytology is occasionally helpful though.

What are the TWO most practical ways to diagnose lymphosarcoma?

1. Clinical signs

2. Necropsy

What are the THREE serology tests you can use in lymphosarcoma cases?

1. AGID (specific and sensitive)

2. RIA

3. ELISA

What does a positive serology for lymphosarcoma tell you?

They are INFECTED, not that they have LSA (something is going on, but not necessarily confirmatory test- can be supportive of dx)

What is the best way to prevent lymphosarcoma? Control?

Prevent: decrease transmission (minimize blood; manage colostrum/milk)

Control: cull positives

What Retrovirus of the subclass Lentivirinae is a pathogen in search of disease?

Bovine immunodeficiency virus (BIV)

Is BIV more common in beef or dairy?

What are TWO major consequences of this?

Dairy

1. Failure to respond to conventional therapies for common diseases

2. Increased culling

What are the TWO major Retroviruses of Lentivirus subclass that infect sheep and goats?

1. Caprine arthritis-encephalits (CAE)

2. Ovine progressive pneumonia (OPP)/Maedi-Visna

Maedi means —- and Visna means —-, indicating this disease is —- in nature.

Dyspnea

Wasting

Chronic

True or False: OPP has a worldwide distribution and a seroprevalence of 30% in the US.

True!

What are the THREE major mechanisms of transmission for OPP?

1. Respiratory secretions

2. Colostrum

3. In utero

What are the THREE major clinical signs of OPP?

1. Chronic active inflammation of lungs, lymph nodes, joints, mammary gland, or CNS

2. Progressive, chronic pneumonia

3. Secondary bacterial infections (C. Pseudotuberculosis)

What kind of sheep are most affected with pneumonia in OPP?

How do they breathe?

What is another major associated clinical sign?

Adults

Rapid and shallow

Lose weight

What are the TWO major preventions/controls for OPP?

1. Test and cull (AGID)

2. Remove lambs from infected ewes before nursing

True or False: There is a vaccine for OPP, but it has limited efficacy and is not recommended.

False! There just isn't a vaccine. Lol

What are the THREE forms of CAE?

1. Neurologic

2. Arthritis

3. Mastitis

True or False: CAE is a chronic, progressive single joint or multiple-joint degenerative arthritis that affects adult goats, usually at a year old, except encephalitis in kids. It also may involve bursae.

True!

True or False: If arthritic disease is present in CAE, it must be the only detectable clinical sign.

False! Arthritic disease may be present ALONE or WITH SIGNS like mastitis, encephalomyelitis, and pneumonia.

CAE is latent in —- and replicates within —-.

Monocytes

Macrophages

CAE has a predilection for macrophages in what FOUR major locations?

1. Synovium

2. Lung

3. Mammary gland

4. CNS

What are the TWO major ways CAE can be transmitted?

1. Colostrum/milk (dam to offspring)

2. Prolonged direct contact or needles

True or False: CAE has a seroprevalence of 22-49% in individual animal prevalence and 73% of herds have an infectious goat. 35% of infected animals have clinical signs.

True!

CAE prevalence is higher in what kind of goat?

Dairy goat

What is the most common site of CAE, which begins as a lameness without swelling and may show swelling without lameness?

Carpal joints

True or False: CAE may develop ankylosis, interstitial pneumonia, hard udder mastitis, and weight loss.

True!

What are the FOUR diagnostics used for CAE?

1. Serology- AGID (exposure only)

2. Histopath of synovium

3. PCR tissue/blood

4. ELISA

What are FOUR treatments of CAE?

1. Supportive care

2. Proper foot care

3. Reduce distance to feed/water/shelter

4. Oral NSAIDs (phenylbutazone, aspirin)

What are the FIVE best ways to prevent CAE?

1. Separate kids from does at birth (feed pasteurized goat/cow colostrum; milk replacer)

2. Maintain closed herd; serotest any new introductions (AGID/PCR)

3. Serotest/segregate positives from negatives or cull all positives

4. Repeated serotesting

5. Keep segregated

What is the chronic, suppurative lymphadenitis of sheep and goats?

Caseous lymphadenitis

What is the major causative agent of caseous lymphadenitis (CL)?

Corynebacterium pseudotuberculosis

How does pus appear in CL?

Thick, white, malodorous (green tinge possible- onion ring appearance)

True or False: Caseous lymphadenitis is not zoonotic, but highly contagious amongst sheep and goats.

False! caseous lymphadenitis IS zoonotic.

What is the #1 cause of condemnation of ewe carcasses at slaughter?

Caseous lymphadenitis

What are the TWO major forms of CL?

Internal and external

Where does internal CL typically develop?

Pulmonary or mediastinal abscesses; lungs/kidney/liver/GI

What are the TWO major clinical signs of internal CL?

1. Weight loss (chronic inflammatory disease)

2. Infertility

How does external CL typically present?

Thick-walled abscess with onion-layered appearance to abscess capsule

Where does external CL typically develop?

Peripheral lymph nodes (prescap, mandibular, parotid)

You should think of —- with internal CL and —- with external CL.

Sheep

Goats

What are the 6 major causes of weight loss in small ruminants?

1. Parasites

2. Johne's disease

3. Caseous lymphadenitis

4. CAE/OPP

5. Dental problems

6. Nutrition

What are the FOUR possible treatments of CL if not culled?

1. Isolate until healed

2. Lance abscess -> flush -> collect exudate and discard sealed

3. Penicillin x3-5d after lancing

What are the FIVE major preventative measures for CL?

1. Cull affected animals

2. Depopulate and disinfect

3. Disinfect shearing blades between animals

4. Avoid shearing during peak fly season

5. Vaccinate (reduce incidence/severity- NOT eliminate)

What are the TWO major vaccine options for CL, especially for show animals?

1. Caseous DT

2. Case-Bac