Illini DairyNet Papers
TAKE HOME MESSAGES
- If your cattle are experiencing unexplained infertility including and early embryonic deaths, check your herd for Lepto hardjo.
- If you find one positive cow for Lepto hardjo, vaccinate the whole herd with the new hardjo-bovis vaccine including young calves.
- Cows chronically infected with the organism may clear up if antibiotics are administered before permanent damage is done to the reproductive tract.
WHAT IS THIS BUG, WHERE’D IT COME FROM AND WHAT CAN IT DO TO MY HERD?
Did you ever wonder what the L5 stood for in all those 9-way cattle vaccines? The “L” stands for Leptospirosis. But why does Lepto account for almost 50% of the “way” in 9-way? Well, there are five common serovars or types of Lepto that are included in the bacterin. This is not to imply that Lepto is the most important antigen included in multivalent vaccines, but simply that the vaccine companies count each serovar as a unique antigen included in their product.
Leptospirosis is a bacterial disease that affects humans and animals. In humans, signs of leptospirosis include high fever, severe headache, chills, muscle aches, and vomiting, and may include jaundice (yellow skin and eyes), red eyes, abdominal pain, diarrhea, or a rash. In cattle, acute clinical disease occurs more often in young calves, but all ages may be affected. Cattle may develop a high fever of 104° to 107°F, depression, loss of appetite, decreased milk production, and weakness. Hemoglobinuria (coffee-colored urine), anemia, icterus (jaundice), and bloody milk are also seen. In lactating cows, milk production may cease altogehter. The milk is usually abnormal and may contain thick yellow or reddish clots. Abortion, mummification or stillbirth may be the only clinical sign reported. This usually occurs two to five weeks after initial infection.
Each of the five serovars is associated with one or more key maintenance hosts (Table 1). Transmission of infection among maintenance hosts is very efficient and the rate of new infections within those populations is relatively high. Infections are usually spread by contact with contaminated urine, placental fluids or milk. Venereal transmission from semen of infected bulls can induce new infections. Incidental hosts are any warm-blooded animal that comes in contact with areas contaminated with urine or secretions of maintenance hosts. So humans would be incidental hosts of Lepto hardjo infections in cattle. Incidental hosts are not important reservoirs of infection and transmission from one incidental host to another is fairly uncommon.
Leptospires are spirochetes and are “kissing cousins” of the Treponema spirochetes that contribute to the hairy heel warts. Certain environmental conditions can increase the likelihood of indirect transmission to cattle. Leptospires prefer warm temperatures and moisture. They can survive for days or weeks outside of a host animal under these conditions. In dry conditions, sweltering or freezing temperatures the organism’s survival is limited. Most leptospirosis outbreaks occur in the spring or fall.
Many producers are confused regarding Lepto hardjo, and rightly so. The term hardjo could stand for “cattle adapted” since cattle are the maintenance host for all forms of this serovar. The most common species of hardjo found in the US is from the Leptosirosis borgpetersenii family. This form is called hardjo-bovis. Leptosirosis interrogans is primarily found in the United Kingdom with a common name of hardjo-prajitno. So why is L. interrogans serovar hardjo ( hardjo-prajitno) included in our common 5-way vaccines in the US? Perhaps history and less strict vaccine development standards play a role here. A recent study tested urine and serum from 15 cows in 44 herds from four different regions in the US. At least one infected cow was found in nearly 60% of the herds and most of the infected cows had hardjo-bovis infections. With hardjo-bovis, one positive cow is diagnostic for an infected herd. Because of the high urinary shedding of the organism into the environment, all animals are considered exposed. If the cattle are naïve, susceptibility to infection is high. In infected herds, it is common to have 30-40% of infected cattle with urinary shedding at any one time.
Infections with hardjo-bovis result in mild clinical disease, but produce a carrier state by setting up camp in the kidneys and creating a long-term urinary shedder. Rarely is the infectio life-threatening to infected cattle. As mentioned previously, leptospirosis can cause reproductive failure in the form of abortions, mummies or stillbirths. Classical lepto abortions occur in the last three months of pregnancy and are typically seen as abortion storms. With hardjo-bovis infections abortions are more sporadic. More insidious ramifications are the fetal losses after conceptions due to persistent infections of the reproductive tract. Infected herds in Illinois have dealt with single digit pregnancy rates for several years before hardjo-bovis was diagnosed. These herds are struggling to maintain cow numbers and cash flow due to the inability to maintain pregnancies and calve fresh cows.
HOW DO I FIND OUT IF MY COWS GOT IT?
Consultation with a herd veterinarian would be prudent if you suspect Lepto hardjo may be a cause of reproductive failure. The veterinarian can help you collect the appropriate samples and get them submitted to laboratories experienced with diagnosing leptospirosis. The Animal Health Diagnostic Laboratory at Michigan State University is one such lab. Submission information can be found at <http://www.ahdl.msu.edu/>. Dr. Carole Bolin, a leptospirologist works at this lab and has developed a procedure for sampling cattle.
- Select 10-15 cows that have been problem breeders (particularly cows that were diagnosed pregnant and then returned to heat shortly after)
- Inject cows with Lasix (5-10 ml, IM, 48 hour milk withholding) and wait 10-15 minutes.
- Be prepared to catch urine in red top tubes labeled with the cows ID.
- Allow the cows to pass urine once or twice in an attempt to empty any urine that may have been stored in the bladder. The goal is to collect newly formed urine (the Lasix will force new urine to be formed), which will “flush” the kidneys and push the organism out. If the urine is yellow, it is stored urine. If the urine is clear, it is new urine.
- Catch urine and then pull a blood sample in another red top tube from the tail vein.
- Chill or refrigerate the samples until they can be mailed to the lab. Collect samples on Monday or Tuesday to assure ample time to mail them and allow the lab to process them prior to a weekend. It is very important the urine arrives as fresh as possible.
The idea behind this collection process is to use the fresh urine to determine if cattle from the herd are shedding leptospires. The serum is used to detect antibody production against the different leptospiral serovars. If breeding bulls are used in the herd, they should be tested as well. Providing the lab with a vaccination history is important to help them interpret the results. Recent vaccination with 5-way lepto will cause increases in antibodies to certain serovars.
HOW DO I KEEP MY COWS FROM BECOMING INFECTED OR WHAT DO I DO IF THEY ARE INFECTED?
Preventing exposure to cattle shedding the organism is the ideal method to reduce the risk of herd-wide infection. While purchasing cattle with unknown lepto status would seem like the most logical source of bringing hardjo-bovis on a farm, several farms in Illinois have developed herd infections without ever bringing in new cattle. Certainly incidental hosts such as wild life and vermin could carry hardjo-bovis onto uninfected farms, but we have no documentation that proves or disproves this theory.
Until recently, vaccination with common US lepto bacterins was ineffective at preventing hardjo-bovis infections. These vaccines contain the hardjo-prajitno serovars that is more common in the UK. Regardless of serovar composition, an “ideal” lepto vaccine should not only prevent kidney infections and urinary shedding into the environment, but also protect the reproductive tract from colonization so fetal infection does not occur. The vaccine should also be able to provide at least 6 months worth of protection and preferably up to one year.
Spirovac ä, produced by a company out of New Zealand (CSL, Inc) has demonstrated the many of the attributes of an “ideal” lepto vaccine. Pfizer, Inc. has purchased the rights to market this vaccine in the US and as of summer 2003, this bacterin in available in the US. Since calves can become infected early in life and develop into chronic shedders, the current recommendations are to begin vaccinating calves as early as 4 weeks of age. A booster dose is required 4 weeks after initial vaccination and an annual booster will maintain protection. Including Spirovac ä in a fresh cow vaccination program will booster immunity at a time prior to attempts to rebreed the cows. Annual boosters at dry off are another option.
If you have cows diagnosed with lepto infections, antibiotic treatment is currently your only option to attempt a cure. Numerous antibiotics have been evaluated in their ability to clear kidney infections, but limited data exists on the ability to remove the organism from the reproductive tract. Oxytetracycline, ceftiofur and ampicillin have been shown to be effective at eliminating kidney infections and urinary shedding. Farms with diagnosed hardjo-bovis infections are using long-acting oxytetracycline at dry-off to make sure any cattle that might be shedding are cleaned out. Coupled with an effective vaccination program that helps prevent cattle from becoming re-infected, antibiotic treatment appears to be beneficial. Attempts to use antibiotics in lactating cattle (perhaps necessary to get them pregnant in the first place) should be done with caution so that violative antibiotic residues do not occur.
Do not forget about the potential for any leptospiral serovar to infect humans. Milkers exposed to cattle shedding organisms in their urine are at the highest risk. New Zealand dairy producers can receive a certificate of vaccination from their veterinarian if the herd is vaccinated against leptospirosis.
Table 1. Summary of Lepto Types
|Lepto serovar||Lepto species||Maintenance host||Cattle Vaccines?|
|Bratislava||L. interrogans||Pigs, horses(?)||No|
|Grippotyphosa||L. interrogans||Raccoons, skunks, opossum||5-way|
|Hardjo ( hardjo-prajitno)||L. interrogans||Cattle||5-way|
|Hardjo ( hardjo-bovis)||L. borgpetersenii||Cattle||New|
|Pomona||L. interrogans||Pigs, cattle, skunks, opossum||5-way|