| dc.description.abstract | The persistence of mild rinderpest in the Eastern Africa region despite continued
eradication efforts has been a subject of concern in recent years among the wildlife
conservation, livestock production, and scientific communities. The current study has
examined the role that wildlife play in the transmission dynamics of the disease, by
characterizing the pathology of two recent isolates of rinderpest virus (RPV) in common
warthogs (Phacochoerus africanusy; African cape buffaloes (Syncerus caffer) and
indigenous cattle (Bas indicusi.
Six (6) wild buffaloes, 13 wild warthogs, and 19 indigenous cattle were used in this study
involving kudu/Bov/BKN2 and RBKIWP/861l isolates belonging to the African lineages
U and I, respectively, ofRPV. Four of the warthogs and four of the cattle were inoculated
parenterally with 1043 TCIDso of the African lineage II isolate of RPV. TIle inoculated
warthogs were housed in contact with four (4) naive cattle and two (2) naive warthogs.
The inoculated cattle were similarly kept in contact with four (4) naive warthogs and two
(2) naive cattle. Two other warthogs were inoculated parenterally with a similar dose of
the virulent Kabete '0' strain of RPV belonging to the Asian type lineage to serve as
positive controls. Another group of fourt 4) cattle was inoculated parenterally with 1048
TCIDso of the African lineage I (RBKIWP/86/l) isolate of RPV and two of these cattle
were kept in contact with four naive wild buffaloes and three (3) naive cattle. Two
animals of each of the three species were parenterally inoculated with a placebo
comprising of minimum essential medium (MEM) devoid of RPV and kept separate as
uninfected controls.
Cuulc were clinically examined and sampled daily starting from the initial day to the time
of necropsy on days 5 to 13, or at convalescence on day 22. Buffaloes and warthogs were
chemically immobilized, examined, and sampled on the initial day and then Oil alternate
days starting from days 3 to 9 depending on the group. Blood samples were taken in
tubes coated with ethylene-diamine tetra-acetic acid (EDT A) lor haematological analysis.
The inoculated animals were euthanised for necropsy at the early and late stages of the
disease from day 5 to day 13 after inoculation. One each of the uninfccted control cattle
and warthogs were also euthanised for necropsy along with the inoculated ones. One sick
in-contact warthog was euthanised for necropsy 22 days after being housed with others
inoculated with the African lineage" isolate of RPV. Representative tissue samples were
obtained from euthanised animals and preserved in 10% neutral buffered formalin. The
tissues were then processed, stained with haematoxylin and eosin (I J&E), and examined
under the light microscope using the standard procedure.
The African lineage 11 isolate of RPV induced a mild disease in the inoculated groups of
warthogs and cattle as well as in the warthogs that were kept in contact with the latter.
Ilowever, the virus induced a moderately severe disease in the group of warthogs that
were kept in contact with inoculated ones. The African lineage I isolate of RVP induced a
mild clinical disease in both the inoculated and in-contact cattle as well as in lite illcontact
buffaloes. The virulent Kabete "0" strain 011 the other hand induced a severe,
rapidly fatal disease in the inoculated warthogs. The disease induced by the various
strains was clinically characterized by oculonasal discharges. stomatitis or varying
degrees, fever in a few cases, and rarely, diarrhoea. In addition, cyanosis of the skin,
vcscicular dermatitis ami inflammation or joints were observed ill warthogs at varying
degrees of frequency. Transient leucopaenia was the mC11n haematological change
induced by the different isolates while the main gross lesions were congestion of the
gastrointestinal mucosa with ulceration in two cases, and congestion of lymph nodes and
Peyers' patches. The main histological lesions induced ill warthogs and cattle by the three
isolates of RPY were varying degrees of epithelial necrosis mostly affecting the mucosa
of the gut and lyrnphocytolysis in lymphoid tissues. These: were occassionally
accompanied by formation of syncytia and eosinophilic intracytoplasmic inclusion bodies
and often infiltrated with neutrophils and macrophages,
These findings showed that warthogs are susceptible to the wildlife-derived African
lineage 1I (kudulBovIBKN2) isolate of RPY developing mild to moderately severe
disease depending on the mode of transmission. They are capable of transmitting the
virus to cattle as well as contracting it from cattle resulting in mild disease. They are also
capable of transmitting it to other warthogs resulting in moderately severe disease that
may be fatal in a proportion of infected warthogs due to secondary complications.
The results from this study rsuggest that wildlife plays an important role in the
epidemiology of rinderpest but further research is needed to clarify the dynamics
involved in the maintenance and persistence of the disease. | en |
