Page 96 - Journal of Special Operations Medicine - Spring 2014

Table 3 Number of Positive Samples to Antigen or Antibody in
Canine Blood Samples Collected in the City of Cartagena.
Antigen or
Antibody
Positive/
Causative Organism All Tested Dogs Prevalence
At least one organism 84/100 84%
Ehrlichia canis (total) 80/100 80%
Anaplasma phagocytophilum 51/100 51%
(total)
Ehrlichia canis (alone) 30/100 30%
Anaplasma phagocytophilum 1/100 1%
(alone)
E. canis +
A. phagocytophilum 49/100 49%
(co-infection) Dr. McCown collecting a blood sample from a stray dog.
E. canis + 1/100 1%
A. phagocytophilum +
D. immitis (co-infection)
Borrelia burgdorferi 0/100 0%
Dirofilaria immitis 3/100 3%

varying elevations. Both Barranquilla and Cartagena
are coastal cities at sea level with hot, humid year-round
tropical climates. Tropical humid climates provide an
adequate environment for the presence of vectors such
as ticks and mosquitoes. 11,16 In South America, vectors
such as Rhipicephalus sanguineous (brown dog tick),
Ixodes spp. ticks, and the mosquitoes Aedes albopic-
tus and Anopheles spp. are present. 13–15 The presence of
these vectors is of significance since R. sanguineus is the
primary vector for E. canis, and Ixodes spp. ticks are
vectors for A. phagocytophilum and B. burgdorferi. 17–19 Dr. Wilder Cardona collecting a blood sample
from a shelter dog in Barranquilla.
Mosquitoes such as Aedes spp. and Anopheles spp. are
capable to transmit D. immitis, and mosquitoes of these
7
genera have been reported in Ecuador and Colombia. 20,21 positive test result is decreased under the influence of
a low prevalence, and a lower positive predicted value
All samples collected in this surveillance were negative of a test leads to an increase in the sample size (num-
for B. burgdorferi antibody, and there was a very low ber of animals) needed to test in order to detect disease-
prevalence for D. immitis. This was an interesting find- positive animals. A decreased positive predicted value
ing as the presence of vectors (mosquitoes and ticks) of a test and a higher sample size make more difficult
and diagnostic evidence for the etiologic agents for these the screening of a disease with a true low prevalence.
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two diseases have been reported in Colombia and other Since sensitivity for D. immitis is crucially influenced by
neighboring and regional countries such as Brazil, Ec- number of adult female parasites, additional diagnostic
uador, Peru, and Argentina. 12–15,22–31 Heartworm disease problems are encountered. In general, it has been sug-
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caused by D. immitis has been reported in the Galapa- gested that co-infection with two or more VBD, like in
gos Islands, in the Amazon regions of Colombia, and this report, could lead to more complex immunological
in neighboring countries of Peru and Brazil, 12,24–26,29 and effects, complicating even further the diagnosis of VBD.
7
similar findings have been reported for Lyme disease Considering all favorable conditions in Colombia, it is
caused by B. burgdorferi. 26,32 It is possible that natural possible to speculate that the prevalence for heartworm
barriers or ecological conditions explain these findings. and Lyme disease will rise over time.
However, the presence of favorable climatic conditions
and vectors make VBD more likely to be present. Then, Future surveillance, both period and point prevalence
33
it is more likely that heartworm and Lyme diseases are study, is necessary to collect objective numbers to deter-
present at a low prevalence. The predictive value of a mine if the prevalence for these diseases is rising, and to

88 Journal of Special Operations Medicine Volume 14, Edition 1/Spring 2014