The economic damage of leptospirosis in the livestock industry is believed to be considerable.

Thus, the study titled “Molecular epidemiology of Pathogenic Leptospira spp. among Large Ruminants in the Philippines”, was conducted. It was meant to determine the local prevalence and carrier status of leptospirosis among water buffalo and cattle using molecular techniques and to assess the risk factors of acquiring leptospirosis in these animals.

The research team was composed of Dr. Marvin A. Villanueva, Dr. Claro N. Mingala, Dr. Michelle M. Balbin, Dr. Chie Nakajima, Dr. Norikazu Isoda, Dr. Yasuhiko Suzuki, and Dr. Nobuo Koizumi.

What leptospirosis is

Leptospirosis is an important re-emerging zoonotic disease worldwide, and is predominantly found in developing countries with tropical or subtropical climates.

It is caused by gram-negative spirochetes from the genus Leptospira which is divided into pathogenic and non-pathogenic species.

Pathogenic leptospires are carried by most mammalian species such as wild, domestic and farm animals, the experts said.  They can transmit infection to humans and other animals either by direct contact with the urine of a carrier animal or indirectly through urine-contaminated environment.

In livestock, leptospirosis is an important cause of decreased animal production as a result of infection by a variety of pathogenic Leptospira serovars or species.

Cattle are known to maintain serovar Hardjo (L. borgpetersenii serovar Hardjo subtype Hardjobovis and L. interrogans serovar Hardjo subtype Hardjoprajitno) that often leads to subclinical and persistent infection of the reproductive tract.

Bovine leptospirosis can create serious economic losses in the livestock industry. It can cause abortions, stillbirths, infertility, reduced milk yield, mortality in calves, and decreased daily weight gain of the animal. 

Findings and significance

The researchers collected urine samples of 729 water buffalo and 102 cattle from 21 farms during the conduct of the study in 2013 to 2015 and were subjected to flaB-nested polymerase chain reaction (PCR) to detect pathogenic Leptospira spp.

Leptospira flaB was detected in both species with a detection rate of 16.1%.

Based on the results of the study, Leptospiral DNA was mainly detected in samples from animals managed in communal farms. Sequence analysis of partial Leptospira flaB in large ruminants revealed the formation of three major clusters with L. borgpetersenii or L. kirschneri.

One farm contained Leptospira flaB sequences from all clusters identified in the study, suggesting that this farm was the main source of leptospires for other farms.

The study suggested that these large ruminants are infected with various pathogenic Leptospira species causing possible major economic loss in the livestock industry as well as potential Leptospira reservoirs that can transmit infection to humans and other animals in the Philippines.

The main goal was to check if PCC’s water buffaloes and cattle were infected with pathogenic leptospires. The researchers found out and detected 16.1%, thus, gave a reminder to regularly monitor the animals if they are infected through PCR as it can possibly affect the production of buffaloes.

Cases like abortion and low milk production of buffaloes may probably occur as well. Further studies are needed to prove this theory.

Further investigations into the effect of Leptospira virulence on the reproductive performance of these animals and elucidation of the role of livestock as either accidental or maintenance hosts are needed to take future actions to prevent leptospirosis from causing risks to public health and economic losses to the large ruminant industry in the Philippines.

A follow-up study on this will be done. Bacteria from the positive cases will be isolated using the urine samples, and the isolates will be subjected to pathogenicity test. The pathogenicity test will be done by infecting the golden Syrian hamster with the Leptospira isolates from infected buffaloes, and its effects will be observed if it can cause disease or death. Hamster is the best animal model for Leptospira study as it shows the same disease manifestation to humans.

More studies to prove that this disease can really cause abortion among buffaloes and can infect humans are needed. The only way to obtain this information is through pathogenicity test.

The Philippines is a leptospirosis-endemic country. However, infection in large ruminants seems neglected which may be due to difficulty in distinguishing clinical signs from other endemic diseases and the lack of appropriate diagnostic laboratory services, especially in rural areas.

Few serological studies were conducted since 1970’s in which two independent studies showed anti-Leptospira antibodies in water buffaloes against serovars Tarassovi, Sejroe and Poi and against serovars Pyrogenes, Pomona and Grippotyphosa, respectively.

The researchers’ recent findings also found evidence of high seroprevalence (48%) and MAT titers against serogroups Mini, Hebdomadis, Tarassovi and Pyrogenes among adult animals, demonstrating a widespread occurrence of leptospirosis in a water buffalo communal farm.

To control leptospirosis, the research team recommended the imposition of strict farm biosecurity measures, periodic testing and treatment of infected herds by giving them antibiotics such as doxycycline, streptomycin, or amoxicillin, and quarantine to prevent the spread of infection from one farm to another.