These images depict a steer calf that had been on feed for 152 days when it was found dead in the home pen. This continues our Post-Mortem Series, in partnership with Feedlot Health Management Services, Okotoks, Alberta.
The team diagnosed this case as a representative example of caudal vena cava thrombosis, which is a common disease of feedlot cattle, particularly later in the feeding period and in specific breeds or classes of cattle.
Caudal vena cava thrombosis in feedlot cattle is most frequently caused by liver abscesses; however, in rare cases, caudal vena cava thromboses can also be caused by septic emboli from other diseases. Liver abscesses originate secondary to translocation of bacteria from the gastrointestinal tract to the bloodstream and ultimately the liver. Ruminal acidosis might induce rumenitis, thereby allowing for bacterial translocation.
Liver abscesses erode into the caudal vena cava and form a septic thrombus. As emboli break away from the thrombus, they often travel to the lungs and/or heart and cause embolic pneumonia and sometimes endocarditis. The emboli in the pulmonary vessels might lead to the formation of aneurysms which often rupture resulting in hemoptysis and/or epistaxis, clinical signs which characterize this disease. Sudden death, with or without clinical signs, is a common outcome in severely affected animals.
In the feedlot, caudal vena cava thrombosis is more commonly observed later in the feeding period when cattle have been exposed to diets contain a high proportion of readily fermentable carbohydrates for a longer period of time.
Caudal vena cava thrombosis (and liver abscessation in general) is observed more commonly in “calf-fed” dairy breeds raised for beef, but this might be due to differences in days of exposure to high-grain diets as opposed to breed differences in susceptibility.
Ante-Mortem Clinical Signs:
Animals with liver abscesses (regardless of caudal vena cava thrombosis) often go undetected or are confused with other diseases until the animal has been slaughtered or succumbs to the disease. However, with respect to caudal vena cava thrombosis, secondary complications could lead to one or more of the following clinical signs:
- Bilateral epistaxis is a common clinical sign and can be foamy in its appearance.
- Signs of respiratory distress can be present including tachypnea, dyspnea and coughing.
- Intermittent fever and nondescript signs of illness might be the only clinical signs in many cases.
- Melena can also be present as the expectorated blood is commonly swallowed.
- Chronic cases might display weight loss and ill thrift.
Management is aimed at control and prevention of subclinical ruminal acidosis and liver abscesses. Like other metabolic diseases, a well-
formulated diet with consistent bunk management, mixing and delivery to minimize daily variations in feed intake is a key for prevention. Providing an appropriate degree of grain processing and roughage coarseness is also important. Various in-feed antimicrobials are effective at reducing the incidence and severity of liver abscesses, which in turn reduces the occurrence of caudal vena cava thrombosis.
Treatment is usually unrewarding, and prognosis is poor. If caudal vena cava thrombosis is highly suspected, humane slaughter or euthanasia might be warranted. However, a definitive diagnosis is often difficult to make with the tools available in a commercial feedlot setting.
Unless the caudal vena cava is thoroughly examined during the post-mortem, many cases of caudal vena cava thrombosis go undiagnosed. It is not uncommon for the pulmonary changes observed to be confused for other types of pneumonia by the layperson. Therefore, a thorough post-mortem examination, including the caudal vena cava, is paramount to making the diagnosis. Post-mortem lesions include:
Upon external examination of the carcass, epistaxis might be observed if a recent pulmonary hemorrhage has occurred.
Upon examining the open chest and cut sections of lung, any of the following lesions can be present:
1. Diffuse multifocal abscesses characteristic of embolic pneumonia in a pattern that is indicative of hematogenous origin.
2. Pallor with areas of aspirated blood and or obvious aneurysm (see Figures 1 and 2).
3. Nondescript interstitial pneumonia pattern.
4. Some cases might have minimal or no lung lesions.
Upon examining the open abdomen, hepatomegaly and/or ascites might be present if the thrombus has sufficiently occluded the vena cava.
Upon incising the liver and examining the vena cava, the pathognomonic lesion consists of an abscess protruding into the vena cava and presence of a septic thrombus (Fig. 3). Additionally, passive congestion of the liver grossly observed as “nutmeg” liver might also be apparent if the vena cava has been occluded.
Post-Mortem Series presented in partnership with Feedlot Health management Services, Okotoks, Alberta. For more information, visit their website at www.feedlothealth.com.
Working with crews at client operations, Feedlot Health conducts post-mortem exams on all feedlot and calf-grower mortalities, using a standard protocol for recording the animal’s history, digital images, and post-mortem findings. The group compiles images and post-mortem findings in a central database, for review by the professional team, as an educational tool and to track disease trends within an operation or across their client base.
Check out the Post-Mortem Archive
To view photos and descriptions from previous cases in our Post-Mortem series, visit our archive.
Available cases include: