hosts acquiring a systemic infection upon direct or
indirect exposure to the urine, blood or tissue of an
infected animal. Leptospirosis seems to have been
less well studied in wildlife - in epidemiological as well
as many other aspects of the disease. This article
will deal with the findings of a few recently published
articles on leptospirosis with emphasis on wildlife.
Classification of the organism
Conventional classification of Leptospira is based on
serological criteria dividing them into two species the pathogenic Leptospira interrogans sensu lato and
the saprophytic Leptospira biflexa sensu lato. More
than 60 serovars have been described for Leptospira
biflexa.
Currently more than 250 serovars separated into 25
serogroups are recorded Leptospira interrogans. The
serological classification system is also complemented
by a genotypic classification, in which 21 genetic
species are currently recognized, which would include
pathogenic, intermediate and non-pathogenic (or
saprophytic) species.
Epidemiology
The epidemiology of leptospirosis is complex and
transmission of infection involves recirculation of
the pathogens among domestic and wild animal
reservoirs. Rodents are recognized as one the most
important sources of infection through persistent
renal carriage stages resulting in urinary shedding
of Leptospira. Multiple factors in complex systems
determine the occurrence of epidemic outbreaks in
humans or animals. Weather-related threats, such
as the El Niño phenomenon, high rainfall season,
flooding, environmental disasters, water consumption,
water sports and occupational exposure may be
associated with outbreaks of leptospirosis.
As fresh water has been considered a source of
leptospirosis the survival and the preservation of
the virulence of pathogenic Leptospira spp were
investigated by Andre-Fontaine et al (2015) - in five
still waters with various pH and mineral profiles.
They found the mean survival was 130 days for
storage at 4 °C, 263 days at 20 °C, and 316 days at
30 °C. Pathogenic strains remained fully virulent
and were able to induce lethal disease in gerbils
even when the pH of the contaminated waters
decreased to < 6. This study confirmed that despite
unfavourable storage conditions (cold and nutrientpoor acidic waters), the survival and virulence of
pathogenic Leptospira spp was fully preserved over at
least 20 months.
The rise in global travel and ecotourism has also led to
dramatic changes in the epidemiology of leptospirosis
and this was reviewed in an article by Bandara et al
(2014). Despite decreasing prevalence of leptospirosis
in endemic regions, previously non-endemic countries
are now reporting increasing numbers of cases due
to recreational exposure. In global context, the
disease is widespread and considered as emerging or
re-emerging, according to the geographical area and
time, or as neglected.
Lindsey et al (2009) reported wildlife ranching to be
increasingly recognised as a productive form of land
use on marginal lands where alternatives such as
agriculture are far less viable. Other developments
were legislative changes during the 1960–70s which
granted landowners the right to utilize wildlife on
their land. Due to a combination of a rising demand
for tourism and safari hunting, recurrent droughts,
overstocking with livestock blamed for range
degradation and reduced productivity which coincided
with declining state subsidies for livestock production
it has resulted in a huge shift from livestock farming
to wildlife ranching in many parts the South African
region.
Citing Zimbabwe, South Africa and Namibia as
examples: In Zimbabwe 1,000 wildlife ranches were
developed, covering and area of 27,000 km2 (prior
to the land seizures in 2000), in South Africa 9,000
wildlife ranches covers 205,000 km2 in addition
to 15,000 mixed livestock and wildlife ranches
whilst in Namibia, wildlife ranches and communal
conservancies encompass 288,000 km2 .
In many other parts of Africa wildlife numbers may
have declined and habitat may have shrunk but
the bush meat trade remains of great economic
2016
MARCH
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