A few years ago, many cattle producers in the heartland had never heard of anaplasmosis. But now, when Kansas State University Extension planned a one-day seminar on the cattle disease, registration quickly exceeded the facility’s seating capacity, and the organizers added a webcast of the event to accommodate interested ranchers from Kansas and other states.

Anaplasmosis, associated with the bacteria Anaplasma marginale, is a tick-vectored disease that also can be spread by some biting insects such as flies and mechanically such as through the use of syringes.

In the past, the disease has been most prevalent in the Gulf Coast region and other wet, tick-friendly environments. More recently though, anaplasmosis has appeared and caused economic losses in beef and dairy herds around the country, including the Midwest and arid West.

“In 2015, almost every county in the eastern two-thirds and several far-west counties of Kansas had samples that were tested and found to be anaplasmosis positive,” says Gregg Hanzlicek, DVM, PhD, director of production animal field investigations for the Kansas Veterinary Diagnostic Lab, noting that it’s not unusual for the disease to be found in eastern Kansas but had not been so much a problem in western Kansas until recently. 

“We don’t know if the geography of this disease has changed or if veterinarians and producers are looking harder for it, but it is clear that there are positive herds in a very large percentage of Kansas.”

Hanzlicek says clinical signs, in adult cattle older than two years, tend to appear within six to 70 days following infection, with an average of 28 days. Clinical signs include:

·         Adult cows or bulls found dead in the pasture

·         Lethargy

·         Difficulty breathing (especially when moved)

·         Aggressive behavior

·         Abortion

·         Icterus or jaundice, characterized by yellow membranes in the eye related to an enlarged spleen

·         Fever

·         Weight loss

·         Constipation

Infection occurs through blood transfer, typically from ticks, which serve as the primary vector. Biting flies also can spread the pathogen, as can equipment such as needles used on multiple animals. All ages of cattle can become infected, with younger animals tending to be more resistant to infection than adults.

All recovered animals will remain lifelong carriers, which do not experience clinical disease but can serve as a source of infection for vectors, Hanzlicek says.

Begin with biosecurity

Controlling the disease begins with biosecurity, says Dave Rethorst, DVM, from the Kansas State University Veterinary Diagnostic Laboratory. This includes using testing and quarantine to avoid introducing infected animals into herds, tick- and insect-control efforts, vaccination, ongoing testing and use of feed-grade chlortetracycline (CTC) for treatment and control, particularly during the vector season. “There is not just one right answer,” Rethorst says, adding that each producer must find what strategies fit best for their situation.

The optimal herd plan, Rethorst says, depends on in-herd prevalence, determined through diagnostic testing. Through testing, producers can work with their veterinarians to determine the aggressiveness of their plan, while also documenting a valid veterinarian-client-patient relationship and need for control as required by the FDA’s Veterinary Feed Directive rules.

Breeding stock added to the herd from endemic or non-endemic areas, Rethorst says, should be held in quarantine for 30 to 45 days and tested for anaplasmosis. 

Rethorst stresses the importance of minimizing risk, rather than completely eliminating anaplamosis from herds. Chemo-sterilization using extended CTC treatments is possible, but not practical in commercial herds, he notes.

Vector control, which can minimize the spread of disease, should focus on controlling ticks but also include efforts to control horse fly, deer fly and stable fly populations as needed.

A vaccine is available for provisional use in many states and has demonstrated efficacy in reducing clinical signs of anaplasmosis. The killed vaccine requires two doses the first year and one dose in subsequent years.

Rethorst suggests three possible herd protocols, based on a 25% prevalence verified through testing and an assumption that FDA will allow antibiotic use for “control” to include “prevention” of anaplasmosis.

Herd protocol 1

·         Document prevalence.

·         CTC .5 mg/lbin mineral during vector season.

·         Vector control.

Approximate cost of single-needle injection, diagnostics, medicated mineral for 120 days, insecticide treatment and terrestrial vector control:

·         Year 1: $36 to $41 per cow.

·         Subsequent years: $29 to $34 per cow.

Herd protocol 2

·         Document prevalence.

·         Vaccinate replacement heifers between weaning and breeding (two doses).

·         Vaccinate purchased cows and bulls prior to vector season (two doses).

·         CTC 0.5 mg per pound in mineral during vector season.

·         Vector control.

Approximate cost of single-needle injection, diagnostics, medicated mineral for 120 days, insecticide treatment, vaccination and terrestrial vector control:

·         Year 1: $39 to $44 per cow.

·         Subsequent years: $31 to $36 per cow.

Herd protocol 3

·         Vaccinate replacement heifers between weaning and breeding (two doses).

·         Vaccinate purchased cows and bulls prior to vector season (two doses).

·         Vaccinate cows prior to vector season (2 doses).

·         Annual booster.

·         Vector control.

Approximate cost of single-needle injection, insecticide treatment, vaccination, and terrestrial vector control:

·         Year 1: $41 to $46 per cow

·         Subsequent years: $34 to $39 per cow

Remember the VFD rules

FDA Veterinary Medical Officer Michael Murphy, DVM, JD, PhD reminds producers that use of feed-grade CTC, beginning in January 2017, will require veterinary oversight within the context of a valid veterinarian-client-patient relationship (VCPR). Full implementation of the FDA’s new veterinary feed directive (VFD) rule will end over-the-counter (OTC) sales of medically important antibiotics used in feeds. The list of medically important feed antibiotics transitioning from OTC to VFD beginning January 1, 2017 includes Tetracyclines such as CTC and Oxytetracycline.

The VCPR is a key component of the new VFD rules. Some states have defined VCPR regulations that conform with federal standards, while in other states, producers and veterinarians will need to comply with the federally defined VCPR. FDA provides a current list of state and federal VCPR requirements at fda.gov/AnimalVeterinary/DevelopmentApprovalProcess/ucm460406.htm.

Key elements in the VCPR, as defined by the FDA, specify that the veterinarian must:

·         Engage with the client to assume responsibility for making clinical judgments about patient health.

·         Have sufficient knowledge of the patient by virtue of patient examination and/or visits to the facility where patient is managed.

·         Provide for any necessary follow-up evaluation or care.

 

Sidebar

What anaplasmosis is, and isn’t

Anaplasmosis, says Kansas State University veterinarian Gregg Hanzlicek, DVM, PhD, is not:

·         A typical bacterial disease. It is a Rickettsia disease, with a very narrow choice for therapy, in which the pathogen must parasitize red blood cells to survive.

·         A uniform disease caused by a consistent parasite. There are different serotypes which originated from different areas of the country. Research tells us, Hanzlicek says, that the ability to cause disease and the response to therapy may be quite different for the different serotypes.

·         A disease that goes away if the animal survives clinical disease.

Anaplasmosis is:

·         A disease with different clinical outcomes based on the age of cattle infected.

·         A disease that can be spread in multiple ways. Ticks are a host where the male tick can be a carrier in which the disease replicates. Flies can pass the disease by mechanical means through carrying infected red blood cells between cattle. We can spread the disease through fomites such as injection needles, dehorners, and implant needles.

·         A disease for which some of our thinking has been informed by older studies that used relatively insensitive tests.

·         A disease with limited data related to the efficacy of treatment and control programs.