Bruce H. Noden

Mapping of Schistosomiasis and Soil-Transmitted Helminths in Namibia: The First Large-Scale Protocol to Formally Include Rapid Diagnostic Tests

Background Namibia is now ready to begin mass drug administration of praziquantel and albendazole against schistosomiasis and soil-transmitted helminths, respectively. Although historical data identifies areas of transmission of these neglected tropical diseases (NTDs), there is a need to update epidemiological data. For this reason, Namibia adopted a new protocol for mapping of schistosomiasis and geohelminths, formally integrating rapid diagnostic tests (RDTs) for infections and morbidity. In this article, we explain the protocol in detail, and introduce the concept of ‘mapping resolution’, as well as present results and treatment recommendations for northern Namibia. Methods/Findings/Interpretation This new protocol allowed a large sample to be surveyed (N = 17 896 children from 299 schools) at relatively low cost (7 USD per person mapped) and very quickly (28 working days). All children were analysed by RDTs, but only a sub-sample was also diagnosed by light microscopy. Overall prevalence of schistosomiasis in the surveyed areas was 9.0%, highly associated with poorer access to potable water (OR = 1.5, P<0.001) and defective (OR = 1.2, P<0.001) or absent sanitation infrastructure (OR = 2.0, P<0.001). Overall prevalence of geohelminths, more particularly hookworm infection, was 12.2%, highly associated with presence of faecal occult blood (OR = 1.9, P<0.001). Prevalence maps were produced and hot spots identified to better guide the national programme in drug administration, as well as targeted improvements in water, sanitation and hygiene. The RDTs employed (circulating cathodic antigen and microhaematuria for Schistosoma mansoni and S. haematobium, respectively) performed well, with sensitivities above 80% and specificities above 95%. Conclusion/Significance This protocol is cost-effective and sensitive to budget limitations and the potential economic and logistical strains placed on the national Ministries of Health. Here we present a high resolution map of disease prevalence levels, and treatment regimens are recommended.

County Scale Distribution of Amblyomma americanum (Ixodida: Ixodidae) in Oklahoma: Addressing Local Deficits in Tick Maps Based on Passive Reporting

ABSTRACT Geographic distribution records for the lone star tick [Amblyomma americanum (L.)] in the peer-reviewed literature are incomplete for Oklahoma, preventing accurate disease risk assessments. To address this issue and document the presence of A. americanum in available habitats throughout the state, county-scale tick records published in U.S. Department of Agriculture—Cooperative Economic Insect Reports and specimens maintained at the K.C. Emerson Entomology Museum, Oklahoma State University, were reviewed. In addition, dry ice traps and tick drags were used to collect adult and nymphal A. americanum from throughout the state. Review of published USDA reports and the local museum collection documented A. americanum in 49 total counties (35 and 35, respectively). Active surveillance efforts confirmed the presence of this tick in 50 counties from which this species had not been previously reported to be established, documenting A. americanum is established in 68 of the 77 (88.3%) counties in Oklahoma. Taken together, these data verify that A. americanum ticks are much more widespread in Oklahoma than reflected in the literature, a phenomenon likely repeated throughout the geographic range of this tick in the eastern half of North America.

Vector-borne diseases of small companion animals in Namibia: Literature review, knowledge gaps and opportunity for a One Health approach

Namibia has a rich history in veterinary health but little is known about the vector-borne diseases that affect companion dogs and cats. The aim of this review is to summarise the existing published and available unpublished literature, put it into a wider geographical context, and explore some significant knowledge gaps. To date, only two filarial pathogens (Dirofilaria repens and Acanthocheilonema dracunculoides) and three tick-borne pathogens (Babesia canis vogeli, Hepatozoon canis and Ehrlichia canis) have been reported. Most studies have focused solely on dogs and cats in the urban Windhoek and surrounding areas, with almost nothing reported in rural farming areas, in either the populous northern regions or the low-income urban areas where animal owners have limited access to veterinary services. With the development of several biomedical training programmes in the country, there is now an excellent opportunity to address zoonotic vector-borne diseases through a One Health approach so as to assess the risks to small companion animals as well as diseases of public health importance.

Sylvatic Infestation of Oklahoma Reptiles with Immature Ixodes scapularis (Acari: Ixodidae)

ABSTRACT Reptiles were collected in nine counties in Oklahoma from September 2002 to May 2004 and examined for Ixodes scapularis (Say) larvae and nymphs to determine seasonal incidence and prevalence of these ticks. In total, 209 reptile specimens consisting of nine species of lizards and seven species of snakes were collected. Plestiodon fasciatus (L.) was the most numerous species collected (55%) followed by Sceloporus undulatus (Latreille) (17%) and Scincella lateralis (Say) (11%). Less than 10 individuals were collected for all remaining reptile species. The infestation prevalence of I. scapularis on all reptile specimens collected was 14% for larvae and 25% for nymphs. Larvae were found on lizards from April until September and peaked in May, while nymphs were found from March until September and peaked in April. I. scapularis larvae (84%) and nymphs (73%) preferentially attached to the axillae/front leg of P. fasciatus. Two chigger species, Eutrombicula splendens (Ewing) and Eutrombicula cinnabaris (Ewing), were found on 2% of the reptiles collected. No ectoparasites, including ticks, were obtained from the seven species of snakes collected.

Low seroprevalence of antibodies to Toxoplasma gondii in blood donors in central Namibia

AbstractAlthough emphasis has been placed on research relating to human immunodeficiency virus (HIV), tuberculosis and malaria, several researchers in Africa are focusing on other threats to human health, such as neglected tropical diseases. Toxoplasma gondii is a possible neglected tropical disease in Namibia, although the country has a diversity of climate, ranging from tropical in the north to semi-desert in the south. Except for one study in 1978, no recent studies have determined the burden of T. gondii infection in Namibia. Three hundred and twelve convenience samples were collected from volunteer blood donors in central Namibia. Donors provided informed consent to participate in the study, and 5 ml blood was collected. Demographic information was collected by means of a questionnaire. Serum was analysed using Captia™ T. gondii immunoglobulin G (Ig) G enzymelinked immunosorbent assay (ELISA) kit. Only samples that tested positive or equivocal for IgG antibodies were then tested for IgM antibodies us...

PREVALENCE OF BABESIA SPP., EHRLICHIA SPP., AND TICK INFESTATIONS IN OKLAHOMA BLACK BEARS (URSUS AMERICANUS)

Abstract American black bears (Ursus americanus) are commonly infested with ticks throughout their range, but there are few surveys for tick-borne disease agents in bears. To characterize tick infestations and determine the prevalence of current infection with Babesia spp. and past or current infection with Ehrlichia spp. in newly re-established populations of black bears in east central and southeastern Oklahoma, US, we identified adult (n=1,048) and immature (n=107) ticks recovered from bears (n=62). We evaluated serum and whole blood samples from a subset (n=49) for antibodies reactive to, and characteristic DNA fragments of, Ehrlichia spp., as well as characteristic DNA fragments of Babesia spp. Amblyomma americanum, the most common tick identified, was found on a majority (56/62; 90%) of bears and accounted for 697/1,048 (66.5%) of all ticks recovered. Other ticks included Dermacentor variabilis (338/1,048; 32.3%) from 36 bears, Amblyomma maculatum (9/1,048; 0.9%) from three bears, and Ixodes scapularis (4/1,048; 0.4%) from three bears. Antibodies reactive to Ehrlichia spp. were detected in every bear tested (49/49; 100%); maximum inverse titers to Ehrlichia chaffeensis ranged from 64–4,096 (geometric mean titer 1,525). However, PCR failed to identify active infection with E. chaffeensis, Ehrlichia ewingii, or an Ehrlichia ruminantium-like agent. Infection with Babesia spp. was detected by PCR in 3/49 (6%) bears. Together these data confirm that tick infestations and infection with tick-borne disease agents are common in bears in the southern US. The significance of these infestations and infections to the health of bears, if any, and the identity of the Ehrlichia spp. responsible for the antibody reactivity seen, warrant further evaluation.

Active surveillance to update county scale distribution of four tick species of medical and veterinary importance in Oklahoma

ABSTRACT: The incidence of tick-borne disease continues to increase in humans and companion animals in the United States, yet distribution maps for several tick vectors in Oklahoma, including Dermacentor variabilis, Dermacentor albipictus, Ixodes scapularis, and Amblyomma maculatum, are not available or are outdated. To address this issue, county-scale tick records from peer-reviewed literature and passive collections were reviewed for Oklahoma. Additionally, dry ice traps, tick drags, and harvested deer were utilized to actively collect adult ticks throughout the state. Through these methods, D. variabilis, D. albipictus, I. scapularis, and A. maculatum were identified in 88% (68/77), 45.4% (35/77), 66.2% (51/77), and 64.9% (50/77) of the counties in Oklahoma, respectively. Baseline maps were developed for the distribution of D. variabilis and D. albipictus and distribution maps were updated for I. scapularis and A. maculatum. This data confirms that these four species of ticks continue to be widespread within Oklahoma with a western expansion of the range of I. scapularis within the state. These results assist efforts to better understand the epidemiology of the different diseases caused by pathogens transmitted by these tick species within the Great Plains region.

Risk of Encountering Questing Ticks (Ixodidae) and the Prevalence of Tickborne Pathogens in Oklahoma State Parks

Abstract. State parks, used by many for various kinds of recreation, are also places where people and their companion animals are exposed to ticks and tickborne pathogens. While most studies in state parks in the United States have evaluated risk of encounter of Lyme-infected ticks, limited studies have focused on state parks in the Great Plains region where tick-borne rickettsial pathogens are more common. Six state parks in four ecoregions of Oklahoma were surveyed for exposure to questing ticks by flag sampling along hiking trails between April and August 2015, and pooled prevalence of tick-borne pathogens was assessed using polymerase chain reaction (PCR). Exposure to ticks varied among parks by location and month, with an encounter rate of 10.8 ticks per minute at Sequoyah State Park in eastern Oklahoma, to less than one tick per minute at Roman Nose State Park in western Oklahoma. Questing ticks were tested for Rickettsia sp., Ehrlichia chaffeensis Anderson et al. 1992 emend. Dumler et al. 2001, and Borrelia burgdorferi Johnson et al. 1984 emend. Baranton et al. 1992 with pooled prevalence rates between 56 and 0% differing among parks. The greatest risk of encountering ticks was at Sequoyah State Park in May 2015, with pooled prevalence rates of 93.3% (Rickettsia sp.) and 13.3% (E. chaffeensis). Results indicated that risk of exposure to ticks and tick-borne pathogens depended on the state park during summer months. These data could be used by the park system to alert visitors to risk of encountering pathogen-infected ticks in a given state park.

First Record of Aedes japonicus japonicus in Oklahoma, 2017

ABSTRACT In spring 2017, mosquito larvae were collected from 25 sites across eastern Oklahoma as part of a Zika virus vector surveillance effort. Aedes japonicus japonicus larvae were collected from horse troughs at 2 sites in Ottawa County, OK. Identification was made using 1 larva stored in 70% ethanol and 3 adult females reared from the larvae. Another invasive mosquito species, Culex coronator, was detected at 2 different sites, adding 2 additional counties to the 9 where the species had been previously reported. The presence of these invasive species in Oklahoma may have an impact on future regional arbovirus concerns.

Questing Behavior and Analysis of Tick-Borne Bacteria in Ixodes scapularis (Acari: Ixodidae) in Oklahoma

Abstract The blacklegged tick, Ixodes scapularis Say (Acari: Ixodidae), is an economically important tick that affects veterinary and public health, but it can be difficult to collect in Oklahoma. The primary goal of this research was to examine the diel activity of each species to help improve collection methods for future field research and test field-collected I. scapularis for endemic and nonendemic tick-borne bacterial genera in the southern Great Plains region. Questing behavior was observed using caged bioassays over 24-h periods throughout fall and spring, and field collections were conducted throughout the afternoon and evening in different locations across Oklahoma. Blacklegged ticks were found to be more active during late afternoon and evening hours, and more ticks were recovered in pastures in the evening. None of the pools of adult I. scapularis tested positive for Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) or Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae) DNA. Of the 46 pools of I. scapularis tested, 27 (58.7%) were positive for Rickettsia sp. with ticks collected from the same location infected with the same species of rickettsial endosymbionts. Results suggest that sampling times later in the day may benefit off-host recovery of I. scapularis in Oklahoma ecosystems.