448 research outputs found
Toxic effect of herbicides used for water hyacinth control on two insects released for its biological control in South Africa
The integrated control of water hyacinth, Eichhornia crassipes (Martius) Solms-
Laubach (Pontederiaceae) has become necessary in South Africa, as biological control
alone is perceived to be too slow in controlling the weed. In total, seven insect
biological control agents have been released on water hyacinth in South Africa. At the
same time, herbicides are applied by the water authorities in areas where the weed
continues to be troublesome. This study investigated the assumption that the two
control methods are compatible by testing the direct toxicity of a range of herbicide
formulations and surfactants on two of the biological control agents released against
water hyacinth, the weevil, Neochetina eichhorniae Warner (Coleoptera:
Curculionidae) and the water hyacinth mirid, Eccritotarsus catarinensis (Carvahlo)
(Hemiptera: Miridae). A number of the formulations used resulted in significant
mortality of the mirid and the weevil. Products containing 2,4-D amine and diquat as
active ingredients caused higher mortality of both agents (up to 80% for the mirid) than
formulations containing glyphosate. Furthermore, when surfactants were added to
enhance herbicide efficiency, it resulted in increased toxicity to the insects. We
recommend that glyphosate formulations should be used in integrated control
programmes, and that surfactants be avoided in order to reduce the toxic nature of spray
formulations to the insect biological control agents released against water hyacinth.Water Research Commission of South Africa (Project 915/1/01).http://www.tandfonline.com/loi/cbst20hb201
Stochastic analysis of surface roughness
For the characterization of surface height profiles we present a new
stochastic approach which is based on the theory of Markov processes. With this
analysis we achieve a characterization of the complexity of the surface
roughness by means of a Fokker-Planck or Langevin equation, providing the
complete stochastic information of multiscale joint probabilities. The method
was applied to different road surface profiles which were measured with high
resolution. Evidence of Markov properties is shown. Estimations for the
parameters of the Fokker-Planck equation are based on pure, parameter free data
analysis
Tydeid species from domatia bearing plants from South Africa with the description of two new species of the genus Afridiolorryia (Acari: Tydeidae)
The monotypic genus Afridiolorryia Kazmierski was collected from the Democratic Republic of the Congo. Two new species belonging to this genus are described here both collected from Psychotria capensis (Eckl.) Vatke (Rubiaceae), in the Eastern Cape Province, South Africa. A key to all the species of the genus as well as the Tydeidae species found during this survey is given.Centre of Excellence in Tree Health and Biotechnology (CTHB) and Green Matter Fellowship.http://www1.montpellier.inra.fr/CBGP/acarologia/Plant Production and Soil Scienc
The association between elevated troponin levels and all cause 30 day mortality in critically ill patients seen at an Academic Hospital – a prospective cohort study
PURPOSES : Elevated cardiac troponins have been shown to be associated with mortality in critical care, but its utility is not well established, especially in the setting of
renal failure. This study aimed to examine the relationship between an early elevated troponin level and all cause 30 day mortality in critically ill patients, and in the
subgroup of patients with renal failure.
METHODS : Serum troponin levels were collected from all patients referred to a critical care team, be they medical or surgical, within 48 hours of referral. The study was
a prospective cohort over a six month period. Patients’ outcome was followed up to 30 days post enrolment.
RESULTS : A total of 202 patients were enrolled in the study over a period of 6 months. One hundred and thirty one patients survived to 30 days (64.9%). A statistically
significant association with troponin elevation and mortality was found (p = 0.008). Higher levels of troponin were also associated with higher mortality in the subjects
studied. Once adjusted for renal failure, a relative risk of death of 2.27 (p = 0.012) was found with troponin values above 325 ng/L.http://www.oatext.com/Pulmonary-and-Critical-Care-Medicine-PCCM.phpam2018Internal Medicin
Ectoparasite burdens of the common mole-rat (Cryptomys hottentotus hottentotus) from the Cape provinces of South Africa
The members of the African mole-rat family Bathyergidae are widely distributed across sub-Saharan Africa. Despite
their well-studied biology and reproductive physiology, the current knowledge of their ectoparasite fauna is limited and ambiguous due
to recent revisions of the bathyergid taxonomy. The common mole-rat (Cryptomys hottentotus hottentotus) is 1 of the most widely
distributed species of these subterranean rodents. Ectoparasites were collected from 268 common mole-rats at 2 localities (Western and
Northern Cape provinces) in South Africa over the course of 18 mo with the aim to document species richness, prevalence, and
abundance of these ectoparasites. The aggregation of parasite species, sex bias within a species, and seasonal variation in ectoparasite
burdens were investigated. A total of 4,830 individual parasites from 4 mite species (Androlaelaps scapularis, Androlaelaps capensis,
Radfordia ensifera, and 1 undetermined chigger [family Trombiculidae]), 1 flea species (Cryptopsylla ingrami), and 1 louse species
(Eulinognathus hilli) were collected. With the exception of R. ensifera and the chigger, all of these ectoparasites appear to be host
specific either for the host species or the Bathyergidae. Aggregation indices indicated that with the exception of E. hilli, the distribution
of all parasite species was highly aggregated among hosts and sex biased. Seasonal variation in prevalence, abundance, and species
richness was apparent, with greater burdens in the rainy winter season. This is likely related to seasonal variation in abiotic factors but
may also be affected by the timing of host reproduction and dispersal behavior.The NRF-SAR Chair for
Mammalian Behavioural Ecology and Physiology to N.C.B. and a
University of Pretoria Research Fellowship to H.L.http://www.journalofparasitology.org/loi/paraam201
Ectoparasite burdens of the Damaraland mole-rat (Fukomys damarensis) from Southern Africa
Damaraland mole-rats (Fukomys damarensis) of the family Bathyergidae are widely distributed subterranean rodents in sub-Saharan Africa. No parasites have ever been reported for this species and only 1 ectoparasite is described for the entire genus. In the current study ectoparasites were collected from individuals captured at 3 localities in South Africa and Namibia to document the ectoparasite community of F. damarensis, investigate their aggregation patterns and evaluate the influence of season on ectoparasite burden. A total of 2,071 arthropods from 9 mite taxa and 1 louse species (Eulinognathus hilli) were collected from 293 hosts sampled. Of these 5 mite species (Androlaelaps scapularis, A. capensis, A. tauffliebi, Radfordia sp. and unidentified chiggers) and the louse were parasites while the remainder were soil mites. All ectoparasites were highly aggregated and the species richness as well as the prevalence and abundance of 4 of them were significantly greater in summer compared to winter, possibly as a result of seasonal changes in rainfall patterns affecting the ectoparasites and/or host behavior.NRF-SARChI chair for Mammalian Behavioural Ecology and Physiology, the NRF and the University of Pretoria.http://digitalcommons.unl.edu/jrnlparasitologyhb201
The Namaqua rock mouse (Micaelamys namaquensis) as a potential reservoir and host of arthropod vectors of diseases of medical and veterinary importance in South Africa
BACKGROUND : The role of endemic murid rodents as hosts of arthropod vectors of diseases of medical and veterinary
significance is well established in the northern hemisphere. In contrast, endemic murids are comparatively
understudied as vector hosts in Africa, particularly in South Africa. Considering the great rodent diversity in South
Africa, many of which may occur as human commensals, this is unwarranted.
METHODS : In the current study we assessed the ectoparasite community of a widespread southern African endemic,
the Namaqua rock mouse (Micaelamys namaquensis), that is known to carry Bartonella spp. and may attain pest status.
We aimed to identify possible vectors of medical and/or veterinary importance which this species may harbour and
explore the contributions of habitat type, season, host sex and body size on ectoparasite prevalence and abundance.
RESULTS : Small mammal abundance was substantially lower in grasslands compared to rocky outcrops. Although the
small mammal community comprised of different species in the two habitats, M. namaquensis was the most abundant
species in both habitat types. From these 23 ectoparasite species from four taxa (fleas, ticks, mites and lice) were
collected. However, only one flea (Xenopsylla brasiliensis) and one tick species (Haemaphysalis elliptica) have a high
zoonotic potential and have been implicated as vectors for Yersinia pestis and Bartonella spp. and Rickettsia conorii,
respectively. The disease status of the most commonly collected tick (Rhipicephalus distinctus) is currently unknown.
Only flea burdens differed markedly between habitat types and increased with body size. With the exception of lice,
all parasite taxa exhibited seasonal peaks in abundance during spring and summer.
CONCLUSION : M. namaquensis is the dominant small mammal species irrespective of habitat type. Despite the great
ectoparasite diversity harboured by M. namaquensis, only a small number of these are known as vectors of diseases of
medical and/or veterinary importance but occur at high prevalence and/or abundance. This raises concern regarding
the potential of this host as an endemic reservoir for zoonotic diseases. Consequently, additional sampling throughout
its distributional range and research addressing the role of M. namaquensis as a reservoir for zoonotic diseases in
southern Africa is urgently needed.University of Pretoria (EC015-10).Third World Organization for Women in Science(TWOWS) and the National Research Foundation (NRF).http://www.parasitesandvectors.comhb201
Ectoparasites associated with the Bushveld gerbil (Gerbilliscus leucogaster) and the role of the host and habitat in shaping ectoparasite diversity and infestations
Rodents are known hosts for various ectoparasite taxa such as fleas, lice, ticks and mites. South Africa is recognized for its animal diversity, yet little is published about the parasite diversity associated with wild rodent species. By focusing on a wildlife-human/domestic animal interface, the study aims to record ectoparasite diversity and levels of infestations of the Bushveld gerbil, Gerbilliscus leucogaster, and to establish the relationship between ectoparasite infestation parameters and host- and habitat factors. Rodents (n = 127) were trapped in 2 habitat types (natural and agricultural) during 2014–2020. More than 6500 individuals of 32 epifaunistic species represented by 21 genera and belonging to 5 taxonomic groups (fleas, sucking lice, ticks, mesostigmatan mites and trombiculid mites) were collected. Mesostigmatan mites and lice were the most abundant and fleas and mesostigmatan mites the most prevalent groups. Flea and mesostigmatan mite numbers and mesostigmatan mite species richness was significantly higher on reproductively active male than female rodents. Only ticks were significantly associated with habitat type, with significantly higher tick numbers and more tick species on rodents in the natural compared to the agricultural habitat. We conclude that the level of infestation by ectoparasites closely associated with the host (fleas and mites) was affected by host-associated factors, while infestation by ectoparasite that spend most of their life in the external environment (ticks) was affected by habitat type
The Namaqua rock mouse (Micaelamys namaquensis) as a potential reservoir and host of arthropod vectors of diseases of medical and veterinary importance in South Africa
BACKGROUND : The role of endemic murid rodents as hosts of arthropod vectors of diseases of medical and veterinary
significance is well established in the northern hemisphere. In contrast, endemic murids are comparatively
understudied as vector hosts in Africa, particularly in South Africa. Considering the great rodent diversity in South
Africa, many of which may occur as human commensals, this is unwarranted.
METHODS : In the current study we assessed the ectoparasite community of a widespread southern African endemic,
the Namaqua rock mouse (Micaelamys namaquensis), that is known to carry Bartonella spp. and may attain pest status.
We aimed to identify possible vectors of medical and/or veterinary importance which this species may harbour and
explore the contributions of habitat type, season, host sex and body size on ectoparasite prevalence and abundance.
RESULTS : Small mammal abundance was substantially lower in grasslands compared to rocky outcrops. Although the
small mammal community comprised of different species in the two habitats, M. namaquensis was the most abundant
species in both habitat types. From these 23 ectoparasite species from four taxa (fleas, ticks, mites and lice) were
collected. However, only one flea (Xenopsylla brasiliensis) and one tick species (Haemaphysalis elliptica) have a high
zoonotic potential and have been implicated as vectors for Yersinia pestis and Bartonella spp. and Rickettsia conorii,
respectively. The disease status of the most commonly collected tick (Rhipicephalus distinctus) is currently unknown.
Only flea burdens differed markedly between habitat types and increased with body size. With the exception of lice,
all parasite taxa exhibited seasonal peaks in abundance during spring and summer.
CONCLUSION : M. namaquensis is the dominant small mammal species irrespective of habitat type. Despite the great
ectoparasite diversity harboured by M. namaquensis, only a small number of these are known as vectors of diseases of
medical and/or veterinary importance but occur at high prevalence and/or abundance. This raises concern regarding
the potential of this host as an endemic reservoir for zoonotic diseases. Consequently, additional sampling throughout
its distributional range and research addressing the role of M. namaquensis as a reservoir for zoonotic diseases in
southern Africa is urgently needed.University of Pretoria (EC015-10).Third World Organization for Women in Science(TWOWS) and the National Research Foundation (NRF).http://www.parasitesandvectors.comhb201
- …