Lepto Pacifica – New Information

The increasing number of human cases of leptospirosis (lepto) is currently being highlighted by medical professionals.

This increase is being attributed to wetter conditions, additional species becoming clinically affected (we have seen severe cases in lambs over the last 12 months) and the changing species of lepto that are infecting people.

In our cattle herds, particularly dairy, we routinely vaccinate for lepto using a vaccine containing two strains, Pomona and Hardjobovis. While this has significantly reduced the risk of lepto in people, today’s increasing cases in people involve the strains Ballum and Pacifica.

Ballum circulates in rat and mice populations, with spill over into people. The newly identified Pacifica strain circulates in cattle and again spills over into humans and in particular, farmers.

Cattle appear to be the maintenance host for Pacifica as this strain has yet to be found in wildlife.  There are no clinical signs associated with Pacifica infection in cattle. The symptoms in people are severe and the clinical signs are more varied. There can be the classic lepto symptoms of fatigue, high fever, and severe headaches but infected persons may also exhibit “loss of appetite”, “vomiting”, “lost 7kg in 6 days”, “chest pain”, “sore throat”, “sore rib cage”.

In recent years, the need for a higher proportion of hospitalisations when lepto is diagnosed, is being linked to this new strain.

What do we know about Pacifica? It is widespread in NZ dairy herds; 75% of our herds show an immune response against Pacifica when blood tested and 27% of the herds had cows shedding this strain in their urine. At a cow level, the survey indicated 1 in 40 cows in Pacifica infected herds were shedding (10 shedding animals per 400).

Pacifica has not yet been able to be cultured but DNA analysis has confirmed this is a new strain. Pacifica shares almost identical antigens with another strain Tarassovi and this has enabled Virbac to licence in NZ a new 4-way lepto vaccine, containing the strains, Hardjobovis, Pomona, Copenhageni and Tarassovi. This new vaccine will become commercially available in December.

How is the vaccine to be applied? To avoid the risk of redwater (lepto) calves may be vaccinated from as young as four weeks of age and they must receive a second dose four to six weeks after the first. Where the primary vaccination is completed before six months of age, a booster dose at six months of age is essential and thereafter an annual booster is required.

This year given Lepto 4-Way will not be available until December, we are continuing to utilise the 7-in-1 vaccine in dairy herds which combines protection for clostridial diseases with protection for Pomona and Hardjobovis. This 7-in-1 vaccination programme starts around the time of disbudding and will ensure your animals are protected from an occurrence of disease caused by these bacteria.

Over the next quarter we will canvas you as to whether you will up-grade your herd’s protection against Tarassovi following the new vaccine’s release into the market. If you do, then we can discuss the options for protecting your herd.

The options will either be vaccinating all ages of cattle twice, four to six weeks apart or phasing the Tarassovi protected cattle in over several years by initially vaccinating the young stock (rising 1- and rising 2-year-olds).

As for many issues, diseases and our knowledge of them evolves and this new information on lepto Pacifica is a major development which we are to consider carefully if we wish to protect our health.

This article contains a lot of information. Please contact one of our veterinary team if you have any questions.