sometimes affect diagnostic tests, making disease control difficult. Prevention at
each step i.e. entry, transmission and establishment should be done. Early detection
and surveillance with a contingency plan to control or eliminate the disease as
quickly as possible is necessary.
Eradication is possible in some cases (examples given earlier) but it takes a long
time, is difficult and costly, and therefore control is the aim of most disease-related
interventions. Cost should not, however, be the main consideration for attempting
control (Thompson 2014). We should try to ensure that the benefits of control will
outweigh costs, bearing in mind that if eradication is impossible, control may be
required indefinitely. To eradicate any disease, the cost rises as the incidence drops.
One should not lose sight of the fact that infectious disease is likely here to stay.
Disease is also a “population control” and evolutionary driver. It is not only the
disease agents that evolve over time, generating new strains, but the hosts also
evolve to try to cope with infection. Thus, we see huge diversity in mammalian
immune systems, for example. This means that a new disease in a naïve population
may have an initially devastating effect, but over time this can settle to an equilibrium. An example of this is foot and mouth disease, which African buffalo harbour
with few serious consequences. However, domestic cattle are affected negatively
by foot and mouth disease.
Finally, although diseases are unlikely to cause extinctions in populations of
relatively common wild animal species, they can severely affect endangered species
with low populations, and that are already facing numerous other threats, and in such
cases diseases could be the final factor that results in extinction.
Acknowledgements The authors were supported by the South African Medical Research Council
and the National Research Foundation of South Africa. Dr. Roy Bengis and Dr. Harry Biggs are
thanked for helpful suggestions.
References
Aaron L, Saadoun D, Calatroni I et al (2004) Tuberculosis in HIV-infected patients: a comprehensive review. Clin Microbiol Infect 10:388–398. https://doi.org/10.1111/j.1469-0691.2004.
00758.x
Acevedo-Whitehouse K, Duffus ALJ (2009) Effects of environmental change on wildlife health.
Philos Trans R Soc B Biol Sci 364:3429–3438. https://doi.org/10.1098/rstb.2009.0128
Aguirre AA (2009) Wild canids as sentinels of ecological health: a conservation medicine perspective. Parasit Vectors 2:S7. https://doi.org/10.1186/1756-3305-2-S1-S7
Ali S, Gugliemini O, Harber S et al (2017) Environmental and social change drive the explosive
emergence of Zika Virus in the Americas. PLoS Negl Trop Dis 11:e0005135. https://doi.org/10.
1371/journal.pntd.0005135
Baazizi R, Mahapatra M, Clarke BD et al (2017) Peste des petits ruminants (PPR): a neglected
tropical disease in Maghreb region of North Africa and its threat to Europe. PLoS One 12:
e0175461. https://doi.org/10.1371/journal.pone.0175461
Barré-Sinoussi F, Chermann JC, Rey F et al (1983) Isolation of a T-lymphotropic retrovirus from a
patient at risk for acquired immune deficiency syndrome (AIDS). Science 220:868–871. https://
doi.org/10.1126/science.6189183
10 Pathogens of Vertebrate Animals as Invasive Species: Insights from South Africa
269
each step i.e. entry, transmission and establishment should be done. Early detection
and surveillance with a contingency plan to control or eliminate the disease as
quickly as possible is necessary.
Eradication is possible in some cases (examples given earlier) but it takes a long
time, is difficult and costly, and therefore control is the aim of most disease-related
interventions. Cost should not, however, be the main consideration for attempting
control (Thompson 2014). We should try to ensure that the benefits of control will
outweigh costs, bearing in mind that if eradication is impossible, control may be
required indefinitely. To eradicate any disease, the cost rises as the incidence drops.
One should not lose sight of the fact that infectious disease is likely here to stay.
Disease is also a “population control” and evolutionary driver. It is not only the
disease agents that evolve over time, generating new strains, but the hosts also
evolve to try to cope with infection. Thus, we see huge diversity in mammalian
immune systems, for example. This means that a new disease in a naïve population
may have an initially devastating effect, but over time this can settle to an equilibrium. An example of this is foot and mouth disease, which African buffalo harbour
with few serious consequences. However, domestic cattle are affected negatively
by foot and mouth disease.
Finally, although diseases are unlikely to cause extinctions in populations of
relatively common wild animal species, they can severely affect endangered species
with low populations, and that are already facing numerous other threats, and in such
cases diseases could be the final factor that results in extinction.
Acknowledgements The authors were supported by the South African Medical Research Council
and the National Research Foundation of South Africa. Dr. Roy Bengis and Dr. Harry Biggs are
thanked for helpful suggestions.
References
Aaron L, Saadoun D, Calatroni I et al (2004) Tuberculosis in HIV-infected patients: a comprehensive review. Clin Microbiol Infect 10:388–398. https://doi.org/10.1111/j.1469-0691.2004.
00758.x
Acevedo-Whitehouse K, Duffus ALJ (2009) Effects of environmental change on wildlife health.
Philos Trans R Soc B Biol Sci 364:3429–3438. https://doi.org/10.1098/rstb.2009.0128
Aguirre AA (2009) Wild canids as sentinels of ecological health: a conservation medicine perspective. Parasit Vectors 2:S7. https://doi.org/10.1186/1756-3305-2-S1-S7
Ali S, Gugliemini O, Harber S et al (2017) Environmental and social change drive the explosive
emergence of Zika Virus in the Americas. PLoS Negl Trop Dis 11:e0005135. https://doi.org/10.
1371/journal.pntd.0005135
Baazizi R, Mahapatra M, Clarke BD et al (2017) Peste des petits ruminants (PPR): a neglected
tropical disease in Maghreb region of North Africa and its threat to Europe. PLoS One 12:
e0175461. https://doi.org/10.1371/journal.pone.0175461
Barré-Sinoussi F, Chermann JC, Rey F et al (1983) Isolation of a T-lymphotropic retrovirus from a
patient at risk for acquired immune deficiency syndrome (AIDS). Science 220:868–871. https://
doi.org/10.1126/science.6189183
10 Pathogens of Vertebrate Animals as Invasive Species: Insights from South Africa
269