Preparing for livestock health threats after flooding and storms

As hurricane season and severe summer storms bring heavy rainfall and flooding across parts of the United States, livestock owners may face more than damaged fences and muddy pastures. Despite the National Oceanic and Atmospheric Administration's (NOAA) anticipation of a below-normal hurricane season, it's still critical livestock owners make preparations should a disaster or severe rain event occur. Flooding, standing water and environmental disruption can create ideal conditions for a variety of serious livestock health concerns long after the clouds clear.

"Flooding and excess moisture can increase exposure to pathogenic agents commonly found in soil, water and animal waste," said Brandon Dominguez, veterinary services section head at the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL.

"Floodwater picks up all sorts of contaminants as it moves, and warm, wet conditions create an environment where several important livestock pathogens can thrive," he said.

TVMDL offers a range of diagnostic services to help veterinarians and producers identify infectious diseases linked to severe summer weather events, enabling timely interventions that protect herd health and reduce economic losses.

Leptospirosis

One of the most concerning bacterial diseases associated with flooding is leptospirosis. The disease is caused by Leptospira bacteria, which survive best in warm, wet environments and are commonly spread through contaminated water sources.

Heavy rains and flooding can wash urine and other bodily secretions from infected wildlife and livestock into ponds, tanks, and standing water sources used by cattle and other animals.

"Most mammalian species can carry leptospirosis," Dominguez said. "Wildlife often carry the bacteria without showing obvious signs of illness, but we more regularly find cases in dogs and livestock."

In cattle, leptospirosis is particularly concerning because it can cause reproductive failure and significant production loss. In dogs, the disease affects kidney function and may present with clinical signs that include:

• Bloody urine
• Excessive drinking or urination
• Fever
• Weakness or lethargy
• General signs of illness

TVMDL diagnostic options for leptospirosis

TVMDL offers multiple diagnostic options for leptospirosis, including:

• PCR testing to detect Leptospira bacterial DNA
• Serology to identify antibodies against the organism
• Urinalysis to evaluate kidney involvement and inflammation

Dominguez noted that combining tests may provide the most accurate diagnosis.

"Depending on the stage of disease, animals may not yet have antibodies or may not be actively shedding bacteria," Dominguez said. "Sometimes it's beneficial to perform both PCR and serology together."

Salmonellosis

In addition to the challenges posed by leptospirosis, producers may also face increased risk of salmonellosis following flooding and hurricanes. Salmonella bacteria are commonly associated with gastrointestinal disease and can spread more easily when animals are crowded onto limited dry ground or exposed to contaminated feed and water.

"After floods or hurricanes, conditions are often warm, wet and crowded," Dominguez said. "Those are ideal conditions for bacterial spread."

Clinical signs of salmonellosis may include:

• Diarrhea
• Fever
• Dehydration
• Reduced appetite
• Weakness

Some animals may carry and spread the bacteria without obvious illness, increasing the risk of transmission within herds. When signs are absent or subtle, diagnostic testing can help reveal what is happening beneath the surface.

TVMDL diagnostic options for Salmonellosis

To help veterinarians identify and manage salmonellosis cases, TVMDL offers diagnostic tests, including:

• Bacterial culture for detection of Salmonella in feces and additional specimen types
• PCR testing for rapid detection of Salmonella DNA

Fecal culture is often the preferred diagnostic approach because positive isolates can undergo additional typing for disease surveillance purposes.

"When we culture Salmonella, we can send the isolate for typing to better understand what strains are circulating in our region," Dominguez said.

PCR testing may provide increased sensitivity in some cases, particularly when bacterial levels are low.

Clostridial diseases

Severe storms and heavy rainfall can also contribute to clostridial disease outbreaks by disturbing soil and exposing dormant bacterial spores.

Clostridial organisms, including those responsible for blackleg and enterotoxemia, can survive in the environment for long periods through spore formation.

"Heavy rains followed by dry conditions may bring spores closer to the soil surface where grazing animals are more likely to encounter them," Dominguez said.

Furthermore, strong winds from hurricanes may disrupt the environment in ways that increase livestock exposure to clostridial diseases. For example, uprooted trees may bring buried bacterial spores to the surface.

Clostridial diseases often progress rapidly and may cause sudden death in otherwise healthy animals. Signs can vary depending on the specific disease but may include:

• Lameness
• Swelling in muscle tissue
• Severe gastrointestinal disease
• Depression or weakness
• Sudden death

Because many clostridial diseases can progress rapidly, sometimes within only a few hours, prompt veterinary attention and monitoring after a severe weather event is critical to help reduce additional herd losses.

TVMDL diagnostic options for clostridial disease

TVMDL offers several testing options for clostridial diseases, including:

• Fluorescent antibody testing for detection of five histotoxic clostridial species (Clostridium novi/hemolyticum, C. chauvoei, C. sordellii, and C. septicum)
• PCR testing for typing of Clostridium perfringens isolates (A, B, C, D, or E)

These diagnostic tools can help veterinarians differentiate clostridial diseases from other causes of sudden death or illness.

Reducing disease after severe weather

While hurricanes and floods cannot always be avoided, proactivity can help reduce disease risk. Producers should consider:

• Limiting livestock access to standing or contaminated water
• Monitoring animals closely after flooding events
• Reducing overcrowding when possible
• Consulting veterinarians promptly when animals appear ill

"Early testing helps producers and veterinarians make informed decisions quickly," Dominguez said. "That's one of the most important tools we have during severe weather season."

TVMDL encourages veterinarians and producers to contact the laboratory when disease concerns arise following severe weather because diagnostic testing can bring emerging health concerns to light before they spread through a herd and lead to preventable losses.

For more information about TVMDL's diagnostic capabilities visit tvmdl.tamu.edu or call the College Station laboratory at 888.646.5623 or the Canyon laboratory at 888.646.5624.