Thesis (Ph.D. (Public Health))--University of the Witwatersrand, Faculty of Health Sciences, 2012 / Factors associated with the transmission of Kaposi’s sarcoma-associated herpesvirus
(KSHV) are inconclusive. In countries where KS and KSHV are confined to men who have
sex with other men (MSM), KSHV is associated with sexual risk factors. In countries where
KSHV is endemic, it affects adults and children of all ages and irrespective of sexual
orientation, suggesting the existence of non-sexual risk factors for KSHV infection.
In this thesis, three distinct cross sectional studies aiming to define the seroprevalence of
KSHV in South African populations and to identify plausible risk factors for KSHV infection
were undertaken. The studies measured KSHV seropositivity in relation to sociodemographic
factors and HIV status. In children, factors associated with horizontal mother to child
transmission were also explored. In adults KSHV seropositivity was also measured in relation
to sexually transmitted infections and/or measures of sexual behaviour. Calculated risk
factors were expressed as odds ratios (95% confidence interval) for KSHV.
Methods
Mother to Child KSHV seroepidemiology Study: KSHV seroprevalence (reactive to either
lytic K8.1 or latent Orf73) was measured in 1287 children and their 1179 biological mothers.
Association between KSHV seropositivity in children was measured against KSHV
seropositivity and HIV status of their mothers.
KSHV seroepidemiology in women attending antenatal clinics: Antibodies to KSHV lytic
K8.1 and latent Orf73 antigens were tested in 1740 pregnant women attending antenatal
clinics in South Africa in 2001. Information on HIV and syphilis serology, age, education,
residential area, gravidity, and parity was anonymously linked to evaluate risk factors for
KSHV seropositivity. Clinics were grouped by municipal regions and their proximity to the two
main river catchments defined.
Carletonville Community KSHV seroepidemiology Study: Sera from 2103 South African
individuals (862 miners, 95 sex workers, 731 female and 415 male township residents) were
tested for antibodies to KSHV lytic K8.1 and latent Orf73, HIV gonococcus, herpes simplex
virus type 2 (HSV-2), syphilis and chlamydia. Information on social, demographic and highrisk
sexual behaviour was linked to laboratory data.
Results
Mother to Child KSHV seroepidemiology Study: KSHV seroprevalence (reactive to either
lytic K8.1 or latent Orf73) was 15.9% (204 of 1287 subjects) in children and 29.7% (350 of
1179 subjects) in mothers. The risk of KSHV seropositivity was significantly higher in children
of KSHV seropositive mothers compared with those of KSHV-seronegative mothers. The HIV
status of mothers was marginally associated with an increased risk of KSHV seropositivity in
their children (AOR = 1.6, 95% CI: 1.0 to 2.6; P = 0.07). KSHV seroprevalence was
significantly higher in HIV-infected subjects (P = 0.0005), and HIV-infected subjects had
significantly higher lytic and latent KSHV antibody levels than HIV-negative subjects.
KSHV seroepidemiology in women attending antenatal clinics: KSHV seroprevalence
was nearly twice that of HIV (44.6% vs. 23.1%). HIV and syphilis seropositivity was 12.7%
and 14.9% respectively in women without KSHV, and 36.1% and 19.9% respectively in those
with KSHV. Women who were KSHV seropositive were 4 times more likely to be HIV positive
than those who were KSHV seronegative (AOR 4.1 95%CI: 3.4 - 5.7). Although, women with
HIV infection were more likely to be syphilis seropositive (AOR 1.8 95%CI: 1.3 - 2.4), no
association between KSHV and syphilis seropositivity was observed. Those with higher levels
of education had lower levels of KSHV seropositivity compared to those with lower education
levels. KSHV seropositivity showed a heterogeneous pattern of prevalence in some localities.
Carletonville Community KSHV seroepidemiology Study: Overall KSHV and HIV
prevalences were 47.5 and 40%, respectively (P<0.43). The risk of HIV infection was highest
in sex workers followed by female residents and miners, compared with male residents
(P<0.001). HSV-2 infection was highly prevalent (66%) and lower, but still substantial,
prevalence (6–8%) was observed for other sexually transmitted infections (STI). No
significant difference in KSHV infection was observed among the residential groups (P>0.05).
KSHV was not associated with any of the STI or any measures of sexual behaviour.
Conclusion
The findings of these three studies contribute substantially to global KSHV seroepidemiology
and show that in Southern African settings KSHV is associated with non-sexual mode of
transmission. Firstly KSHV is common in very young children up to ten years of age and
increases with age until adulthood. The high prevalence of KSHV in the South African
populations remained evident in all populations. In children, the risk of acquisition of KSHV
was higher among children of KSHV-seropositive mothers than if the mother was KSHV
negative. The association between KSHV and HIV was also noted in the study of pregnant
women attending antenatal clinics and in the mother to child study. However this association
was not evident in the Carletonville population where both KSHV and HIV were highly
prevalent.
In both the adult studies the lack of association between KSHV and syphilis was evident.
KSHV infection was also not associated with other sexually transmitted infections and
measures of sexual behaviour. As expected, the pattern of HIV and STI in sex workers
suggests high rates of high-risk sexual behaviour in this population; however KSHV
seropositivity was the same amongst sexworkers and all the other community groups. This
pattern of the lack of association with high-risk sexual behaviour, particularly in sex workers
and with any markers of STI strongly suggests that the sexual mode does not play a
significant role in KSHV transmission in this South African population. This may also suggest
that KSHV transmission may involve geographical and cultural factors other than sexual
transmission.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/12671 |
| Date | 19 April 2013 |
| Creators | Malope-Kgokong, Babatyi Innocentia |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Format | application/pdf, application/pdf |
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