Heike Lutermann

Arthropod vectors are responsible for a multitude of human and animal diseases affecting poor communities in sub-Saharan Africa. Their control still relies on chemical agents, despite growing evidence of insecticide resistance and environmental health concerns. Biorational agents, such as the entomopathogenic fungus Metarhizium anisopliae, might be an alternative for vector control. Recently, the M. anisopliae isolate ICIPE 7 has been developed into a commercial product in Kenya for control of ticks on cattle. We were interested in assessing the potential of controlling not only ticks but also disease-transmitting mosquitoes and tsetse flies using cattle as blood hosts, with the aim of developing a product for integrated vector management. Laboratory bioassays were carried out with M. anisopliae, isolate ICIPE 7 and isolate ICIPE 30, to compare efficacy against laboratory-reared Anopheles arabiensis. ICIPE 7 was further tested against wild Glossina fuscipes and Rhipicephalus spp. Dose–response tests were implemented, period of mosquito exposure was evaluated for effects on time to death, and the number of spores attached to exposed vectors was assessed. Exposure to 10⁹ spores/mL of ICIPE 7 for 10 min resulted in a similar mortality of An. arabiensis as exposure to ICIPE 30, albeit at a slower rate (12 vs. 8 days). The same ICIPE 7 concentration also resulted in mortalities of tsetse flies (LT₅₀: 16 days), tick nymphs (LT₅₀: 11 days), and adult ticks (LT₅₀: 20 days). Mosquito mortality was dose-dependent, with decreasing LT₅₀ of 8 days at a concentration of 10⁶ spores/mL to 6 days at 10¹⁰ spores/mL. Exposure period did not modulate the outcome, 1 min of exposure still resulted in mortality, and spore attachment to vectors was dose-dependent. The laboratory bioassays confirmed that ICIPE 7 has the potential to infect and cause mortality to the three exposed arthropods, though at slower rate, thus requiring further validation under field conditions.

Rodents from the southern hemisphere are underrepresented in studies of animal personality. In the current study, we assessed personality in 22 wild-caught Namaqua rock mice (Micaelamys namaquensis), a species that is widespread throughout southern Africa. We assessed exploration, aggression and boldness scores and evaluated the effects of intrinsic (i.e., sex) and extrinsic (i.e., captive environment) factors on personality. Rock mice showed personality and behavioural plasticity. While sex alone was not an important factor in the personality of this species, the initial trial differed significantly from subsequent ones, indicative of capture stress and/or subsequent habituation. We found a behavioural syndrome between aggressiveness and exploration, as well as between aggressiveness and boldness scores. Thus, our study extends our knowledge of personality and behavioural syndrome in wild rodents and suggests a role of sex on habituation. The fitness implications of these findings for the study species merit further study in the future.

Transmission of parasites between hosts is facilitated by close contact of hosts. Consequently, parasites have been proposed as an important constraint to the evolution of sociality accounting for its rarity. Despite the presumed costs associated with parasitism, the majority of species of African mole-rats (Family: Bathyergidae) are social. In fact, only the extremes of sociality (i.e., solitary and singular breeding) are represented in this subterranean rodent family. But how did bathyergids overcome the costs of parasitism? Parasite burden is a function of the exposure and susceptibility of a host to parasites. In this review I explore how living in sealed burrow systems and the group defenses that can be employed by closely related group members can effectively reduce the exposure and susceptibility of social bathyergids to parasites. Evidence suggests that this can be achieved largely by investment in relatively cheap and flexible behavioral rather than physiological defense mechanisms. This also shifts the selection pressure for parasites on successful transmission between group members rather than transmission between groups. In turn, this constrains the evolution of virulence and favors socially transmitted parasites (e.g., mites and lice) further reducing the costs of parasitism for social Bathyergidae. I conclude by highlighting directions for future research to evaluate the mechanisms proposed and to consider parasites as facilitators of social evolution not only in this rodent family but also other singular breeders.

Background: Malaria continues to be a leading cause of morbidity and mortality in Africa and conventional malaria control strategies such as indoor residual spraying (IRS) and insecticide-treated bednets (ITNs) are increasingly losing their effectiveness. Consequently, the development of alternative or supplementary strategies is required. One potential strategy is the use of cattle/livestock-administered endectocides to control vector mosquitoes that feed outdoors on livestock. However, since this strategy requires support from local communities and livestock owners consenting for their animals to be treated, it can only be implemented if acceptance by affected communities is sufficiently high. The aim of this study was to assess the social acceptance and practicality of the use of cattle/livestock-administered endectocides in the malaria endemic villages of Vhembe District, Limpopo Province, South Africa, where malaria incidence is high. Methods: Questionnaires were administered in the Vhembe District in 103 livestock-owning households from four villages, namely, Gumbu, Malale, Manenzhe and Bale. The assessment included questions on the acceptability of the strategy, the type and number of livestock owned, distances between houses and kraals (overnight pens) as well as previous use and awareness of endectocides. The results were analysed using descriptive statistics and multinomial logistic regression. Results: The types of livestock owned by the participants comprised, cattle, goats, sheep and donkeys, with the most dominant being goats (n = 1040) and cattle (964). The majority of the participants had their kraals less than 10 meters from their houses. Most participants (72.5%) reported that they were already using chemicals to treat their livestock for parasites. About 33.3% of the livestock owners reported that they or their family members had previous infections of malaria. All participants indicated that they would accept the implementation of the strategy and would give consent for their animals to be treated by endectocides. Conclusions: The use of cattle/livestock-administered endectocides appears to be a feasible and acceptable approach for control of animal-feeding malaria vector species in the malaria endemic villages of Vhembe District in Limpopo Province. This is based on a high percentage of rural residents keeping suitable livestock close to their homes and expressing willingness to use endectocides for mosquito control.

Females of many species discriminate among males when choosing a mate and this can bear indirect and direct benefits including the avoidance of parasite transmission from infested males. In rodents, this may be mediated by androgen hormones that affect the expression of urinary odors. Female choosiness may also vary with a female’s infestation status, with infested females being less choosy. In the current study we tested the preference of cooperatively breeding highveld mole-rat (Cryptomys hottentotus hottentotus) females for male urinary odors from healthy males and those naturally infested with a cestode (Mathevotaenia sp.). Thirty females (15 healthy, 15 infested) were allowed to explore a Y-maze with urine samples from healthy and infested males and the frequency of entering choice arms and chambers as well as the duration spend with each odor sample was recorded. Infestation status did neither affect male body mass, urinary testosterone, nor cortisol levels or the body condition of females. Although overall female activity was not affected by infestation status, infested females entered choice arms and chambers significantly less frequently than healthy females. Surprisingly, healthy females preferred odors from infested males while the opposite was true for infested females, independent of male hormone levels. As the study species lives in groups that tend to share the same infestation status, we suggest that highveld mole-rat females may exhibit a preference for unfamiliar odors, possibly as an indicator of genetic diversity, rather than discriminate between infestation status of males. Similar mechanisms may also play a role in other social species.

Background: Malaria control primarily depends on two vector control strategies: indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLINs). Both IRS and LLIN target indoor-biting mosquitoes. However, some of the most important malaria vectors have developed resistance against the chemical compounds used in IRS and LLINs. Insecticide-induced behavioural changes in vectors, such as increased outdoor feeding on cattle and other animals, also limit the effectiveness of these strategies. Novel vector control strategies must therefore be found to complement IRS and LLINs. A promising tool is the use of cattle-applied endectocides. Endectocides are broad-spectrum systemic drugs that are effective against a range of internal nematodes parasites and blood-feeding arthropods. The aim of this study was to investigate the effect of two endectocide drugs, injectable ivermectin and topical fipronil, on the survival and fecundity of zoophilic Anopheles arabiensis. Methods: Laboratory-reared mosquitoes were allowed to feed on cattle treated with either injectable ivermectin (0.2 mg/kg), topical fipronil (1.0 mg/kg) or saline (control) on days 0, 1, 4, 7, 13, 21 and 25 post-treatment, and mortality and egg production were recorded daily. Results: Compared to controls, the mortality of An. arabiensis increased by 3.52- and 2.43-fold with injectable ivermectin and topical fipronil, respectively. The overall fecundity of mosquitoes that fed on both ivermectin- and fipronil-treated cattle was significantly reduced by up to 90 and 60%, respectively, compared to the control group. The effects of both drugs attenuated over a period of 3 weeks. Injectable ivermectin was more effective than topical fipronil and increased mosquito mortality by a risk factor of 1.51 higher than fipronil. Similarly, both drugs significantly reduced the fecundity of An. arabiensis. Conclusions: This study demonstrates that injectable ivermectin and topical fipronil are able to suppress An. arabiensis density and could help to reduce outdoor malaria transmission. Data from the present study as well as from other similar studies suggest that current-generation endectocides have a limited duration of action and are expensive. However, new-generation, sustained-release formulations of ivermectin have a multi-week, high mortality impact on vector populations, thus holding promise of an effective reduction of outdoor malaria transmission. Graphical

Background Malaria control primarily depends on two vector control strategies; indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLIN). Both IRS and LLIN target indoor-biting mosquitoes. However, some of the most important malaria vectors have developed resistance against the chemical compounds used in IRS and LLIN’s. Insecticides-induced behavioural changes in vectors, such as increased outdoor feeding on cattle and other animals also limit the effectiveness of these strategies. Novel vector control strategies must therefore be found to complement IRS and LLIN’s. A promising tool is the use of cattle-applied endectocides. Endectocides are broad-spectrum systemic drugs effective against a range of internal nematodes parasites and blood-feeding arthropods. The aim of this study was to investigate the effect of two endectocide drugs, ivermectin and fipronil, on the survival and fecundity of zoophilic Anopheles arabiensis. Methods Laboratory-reared mosquitoes were allowed to feed on cattle treated with either ivermectin (0.2 mg/kg), fipronil (1.0 mg/kg) or saline (Control) on day 0, 1, 4, 7, 13, 21 and 25 post-treatment and mortality and egg production were recorded daily. Results Compared to controls, the mortality of An. arabiensis increased 3.52 and 2.43 times with ivermectin and fipronil, respectively. The overall fecundity of mosquitoes that fed on both ivermectin- and fipronil-treated cattle was significantly reduced by up to 90% and 60%, respectively, compared to the control group. The effects of both drugs attenuated over a period of 3 weeks. Ivermectin was more effective than fipronil and increased mosquito mortality by a risk factor of 1.51 higher than fipronil. Similarly, both drugs significantly reduced the fecundity of An. Arabiensis. Conclusions This study demonstrated that ivermectin and fipronil are able to suppress An. arabiensis density and could help to reduce outdoor malaria transmission. The data from the current study as well as other similar studies suggest that current-generation endectocides have limited-duration action and are expensive. However, new-generation sustained-release formulations of ivermectin have multi-week high mortality impact on vector populations, thus holding promise of effective reduction of outdoor malaria transmission.

A deterministic mathematical model for the dynamics of cannabis use in a South Africa metropolis of Durban is proposed and analysed. To the analysis the model, the important threshold parameter ℛ₀ (the basic reproduction number), is determined. It is proved that the model exhibits multiple cannabis persistent equilibria. For ℛ₀ < 1, the model exhibits a backward bifurcation due to double exposure to cannabis sources and re-addiction in the population. More precisely, the locally asymptotically stable cannabis-free equilibrium co-exists with the locally asymptotically stable cannabis persistent equilibrium. Under this situation, the cannabis consumption will remain stay in the population even though ℛ₀ < 1. In the absence of double exposure and re-addiction, it is shown that the cannabis-free equilibrium is globally asymptotically stable (GAS) when ℛ₀ < 1, while the cannabis persistent equilibrium is GAS when ℛ₀ > 1. The model is fitted into the available data and the values of the parameters involved in the model formulation are estimated. Sensitivity analysis of the model, using the parameters involved in the formulation of ℛ₀ , is given. Numerical simulation to support the theoretical analysis of the model is provided.

Members of the flea family Pulicidae have been the focus of many studies due to their significance as diseases vectors of medical and veterinary importance and their cosmopolitan distribution. They often exhibit variation in morphological features that can make correct species identification and management challenging. This may also apply to Xenopsylla brasiliensis (Baker, 1904), an important plague vector. In the current study, we aimed to provide genetic tools for reliable species identification using a DNA barcoding approach. A total of 73 flea specimens was collected from a native host (Namaqua rock mouse, Micaelamys namaquensis) in South Africa and identified morphologically. In addition, we took measurements of 7 morphological characteristics. Subsequently, we successfully generated barcodes of the mitochondrial cytochrome c oxidase subunit I (COI) gene for X. brasiliensis. We validated this approach by comparing our data to COI sequences from Rwandan X. brasiliensis. While sequences from both regions suggested a close relationship between the 2 X. brasiliensis populations, both haplotype and nucleotide diversity were substantially larger for the South African specimens. This may be attributed to human-assisted spread, differences in habitat, and/or host species sampled and merits further study in the future.