Molecular survey of haemoplasmas in shelter dogs and associations with Rhipicephalus sanguineus sensu lato

This study aimed to assess the occurrence of canine haemoplasma infection in domestic dogs and its possible trans‐stadial transmission by Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae) in shelter dogs in Diyarbak?r Province in southeast Turkey. Blood samples (n = 282) collected from domestic dogs were analysed by polymerase chain reaction (PCR) for the presence of canine haemoplasma. Fully engorged nymphs (n = 204) were removed from dogs that were positive for canine haemoplasma by PCR and maintained in an incubator at 28 °C for moulting. Unfed ticks (n = 2185) comprising 2100 nymphs and 85 adults collected from the grounds of the same shelter were also screened. Of 282 dogs, 108 [38.3%, 95% confidence interval (CI) 32.6–44.2] were PCR‐positive for canine haemoplasmas. Mycoplasma haemocanis (Mhc) infection (26.2%, 95% CI 21.2–31.8) was observed in a significantly higher number of dogs than was Candidatus Mycoplasma haematoparvum (CMhp) infection (6.7%, 95% CI 4.1–10.3). Co‐infections were seen in 15 (5.3%, 95% CI 3.0–8.6) dogs. None of the tick specimens examined were found to be positive for haemoplasma. Partial sequences of the 16S ribosomal RNA (rRNA) gene shared 99–100% identity with the corresponding published sequences for Mhc and CMhp. The present results revealed no trans‐stadial transmission of canine haemoplasma species by R. sanguineus s.l. in field conditions.     

Potential role of ATP‐binding cassette transporters against acaricides in the brown dog tick Rhipicephalus sanguineus sensu lato

ATP‐binding cassette (ABC) transporters have been shown to be involved in pesticide detoxification in arthropod vectors and are thought to contribute to the development of drug resistance. Little is currently known about the role they play in ticks, which are among the more important vectors of human and animal pathogens. Here, the role of ABC transporters in the transport of fipronil and ivermectin acaricides in the tick Rhipicephalus sanguineus (Ixodida: Ixodidae) was investigated. Larvae were treated with acaricide alone and acaricide in combination with a sub‐lethal dose of the ABC transporter inhibitor cyclosporine A. The LC₅₀ doses and 95% confidence intervals (CIs) estimated by mortality data using probit analysis were 67.930 p.p.m. (95% CI 53.780–90.861) for fipronil and 3741 p.p.m. (95% CI 2857–4647) for ivermectin. The pre‐exposure of larvae to a sub‐lethal dose of cyclosporine A reduced the LC₅₀ dose of fipronil to 4.808 p.p.m. (95% CI 0.715–9.527) and that of ivermectin to 167 p.p.m. (95% CI 15–449), which increased toxicity by about 14‐ and 22‐fold, respectively. The comparison of mortality data for each separate acaricide concentration showed the synergic effect of cyclosporine A to be reduced at higher concentrations of acaricide. These results show for the first time a strong association between ABC transporters and acaricide detoxification in R.sanguineus s.l.     

Comparative activity of three repellents against the ticks Rhipicephalus sanguineus and Argas persicus

The residual repellent activity of N,N-diethylphenyl-acetamide (DEPA), N,N-diethyl-3-methyl benzamide (DEET) and dimethylphthalate (DMP) against the hard tick Rhipicephalus sanguineus (Latreille) and the soft tick Argas persicus (Oken) from topical application on rabbits and hens respectively in the laboratory have been studied. It was found that a 25% concentration of DEET gave strong repellency (greater than 90%) against larvae and nymphs of R. sanguineus for 15 and 7 days respectively and against A. persicus larvae and nymphs greater than 90% for 11 and 5 days respectively. Strong repellency (greater than 90%) against adults of the hard and soft ticks was observed for 9 and 7 days respectively with 40% DEET. DEPA at 25% concentration showed strong repellency (greater than 90%) against larvae and nymphs of R. sanguineus and A. persicus for 11 and 5 days respectively. Adults of hard and soft ticks were strongly repelled (greater than 90%) for 9 and 5 days respectively by 40% DEPA. DMP was found to be the least effective against all stages of both species of tick.     

First report of amitraz and cypermethrin resistance in Rhipicephalus sanguineus sensu lato infesting dogs in Mexico

Engorged female Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae) were collected from dogs in the state of Yucatán, Mexico. Fourteen tick populations were collected from dogs at seven veterinary clinics, four residential homes and three cattle farms. The larval immersion test was used in the progeny of collected adult females to test susceptibility to amitraz and cypermethrin. Dose–mortality regressions, 50% lethal concentrations (LC₅₀), confidence intervals and slope were estimated by probit analysis. For amitraz, 12 tick populations (85.7%) were classified as resistant and low inter‐population variation in the phenotypic level of resistance was evident [resistance ratios (RRs) at LC₅₀: 1.0–13.0]. For cypermethrin, 12 tick populations (85.7%) were classified as resistant and substantial inter‐population variation in the phenotypic level of resistance was evident (RRs at LC₅₀: 1.0–104.0). Thus, amitraz resistance in R. sanguineus s.l. is common, but generally occurs at low levels; however, alarmingly high levels of cypermethrin resistance are present in R. sanguineus s.l. populations in dogs in Yucatán, Mexico. The intensive use of both acaricides to control ectoparasites on dogs is likely to lead to more serious resistance problems that may cause high levels of control failure in the future.     

Pathogenicity of entomopathogenic fungi to different developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae).

The pathogenicity of 4 species of entomopathogenic fungi (Hyphomycetes species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, and Paecilomyces fumosoroseus) to various developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae) ticks was compared under laboratory conditions. The most virulent isolate, M. anisopliae-108, caused 92-96% mortality to unfed larvae and nymphs on day 7 postinfection (PI) and 100% mortality to unfed adults and engorged females on day 21 PI. The pathogenicity of M. anisopliae-108 to engorged larvae and nymphs was lower--82.6 and 60%, respectively. All tested B. bassiana, M. flavoviride, and P. fumosoroseus isolates were significantly less virulent (P < 0.05) or avirulent toward most life stages of R. sanguineus. The M. anisopliae and M. flavoviride isolates also prevented or reduced the ability of the ticks to lay eggs several days before their deaths. Female ticks infected by the fungi achieved only 11.3-60.8% of their egg-laying capacity compared with the controls.     

Life history of the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in Kenya

We conducted laboratory and field experiments to elucidate the life history of Ixodiphagus hookeri, a parasitoid of the ixodid tick Amblyomma variegatum in Western Kenya. Ixodiphagus hookeri females oviposited in unfed host nymphs as well as engorged nymphs, but rarely in engorged larvae. While I. hookeri developed to adults in engorged nymphs, the eggs laid in unfed nymphs disappeared within 2 days after oviposition. As temperature increased, development time of I. hookeri from oviposition to adult emergence in engorged nymphs decreased from 46 days at 23 °C to 35 days at 28 °C, and their immature survival in engorged nymphs decreased from 67% at 23 °C to 22% at 28 °C. No parasitoid adult emerged from hosts at 30 °C. Individual hosts parasitized by single females produced 42–53 adult wasps, 73% of which were females. As a typical pro-ovigenic species, I. hookeri females had an average of 84 mature eggs at emergence and lived only for a few days. When laboratory-reared, unfed nymphs of A. variegatum were attached to cattle for 4–9 days in subsistence farmers’ fields in Western Kenya, 25% of the engorged nymphs and 4% of the unfed nymphs on cattle were parasitized by I. hookeri, demonstrating that I. hookeri females search for and oviposit in A. variegatum nymphs on cattle. Unlike other strains of I. hookeri that overwinter as eggs in unfed nymphs, I. hookeri could continuously reproduce throughout the year in Western Kenya.     

Field sampling of unfed nymphs ofAmblyomma hebraeum

Unfed nymphs ofAmblyomma hebraeum Koch, 1844 shelter under debris on the soil surface and become active in host-seeking when stimulated with carbon dioxide. The active nymphs are not attracted to sources of carbon dioxide and hence cannot be effectively sampled using static carbon dioxide traps. However, these nymphs will cling to flannelette and can be sampled by flagging. Larger numbers are recovered if the soil surface is sampled using a vacuum device.     

A survey of tick‐borne pathogens in dogs and their ticks in the Pantanal biome,Brazil

Tick and blood samples collected from domestic dogs in the Brazilian Pantanal were tested by molecular methods for the presence of tick‐borne protozoa and bacteria. Among 320 sampled dogs, 3.13% were infected by Babesia vogeli (Piroplasmida: Babesiidae), 8.75% by Hepatozoon canis (Eucoccidiorida: Hepatozoidae), 7.19% by Anaplasma platys (Rickettsiales: Anaplasmataceae), and 0.94% by an unclassified Anaplasma sp. In three tick species collected from dogs, the following tick‐borne agents were detected: (a) B. vogeli, An. platys and Ehrlichia canis (Rickettsiales: Anaplasmataceae), infecting Rhipicephalus sanguineus sensu lato (Ixodida: Ixodidae) ticks; (b) H. canis, an unclassified Anaplasma sp. and Rickettsia amblyommii (Rickettsiales: Rickettsiaceae), infecting Amblyomma cajennense sensu lato (Ixodida: Ixodidae) ticks, and (c) Rickettsia sp. strain Atlantic rainforest, an emerging human pathogen, infecting Amblyomma ovale ticks. Molecular analysis, based on a mitochondrial gene, revealed that the Am. cajennense s.l. ticks of the present study corresponded to Amblyomma sculptum, a member of the Am. cajennense species complex, and that Rh. sanguineus s.l. belonged to the tropical lineage. Whereas dogs are exposed to a number of tick‐borne bacterial and protozoan agents in the Pantanal biome, humans are potentially exposed to infection by spotted fever group rickettsiae (e.g. R. amblyommii and Rickettsia sp. strain Atlantic rainforest) because both Am. sculptum and Am. ovale are among the most important human‐biting ticks in Brazil.     

Analysis of ear side of mobile phone use in the general population of Japan

This study aimed to clarify the distribution of the ear side of mobile phone use in the general population of Japan and clarify what factors are associated with the ear side of mobile phone use. Children at elementary and junior high schools (n = 2,518) and adults aged ≥20 years (n = 1,529) completed an Internet‐based survey. Data were subjected to a logistic regression analysis. In children, due to the tendency to use the dominant hand, we analyzed the factors associated with the use of right ear in right‐handed people. Statistically significant differences were observed only in talk time per call (odds ratio (OR) = 2.17; 95% confidence interval (CI): 1.22–3.99). In adults, due to the tendency to use the left ear, we analyzed factors associated with the use of left ear in right‐handed people. Significant differences were observed in those aged 30–39 years (OR = 2.55; 95% CI: 1.79–3.68), those aged 40–49 years (OR = 3.08; 95% CI: 2.15–4.43), those aged >50 years (OR = 1.85; 95% CI: 1.20–2.85), and in those with a percentage of total talk time when using mobile phones at work of 51–100% (OR = 1.75; 95% CI: 1.21–2.55). We believe that future epidemiological studies on mobile phone use can be improved by considering the trends in mobile phone use identified in this study. Bioelectromagnetics. 39:53–59, 2018. © 2017 Wiley Periodicals, Inc.     

Survival and cause-specific mortality of male wild turkeys across the southeastern United States

Estimating survival and cause-specific mortality of male eastern wild turkeys (Meleagris gallopavo silvestris) is important for understanding population dynamics and implementing appropriate harvest management. To better understand age-specific estimates of annual survival and harvest rates, we captured and marked male wild turkeys with leg bands (n = 311) or bands and transmitters (n = 549) in Georgia, Louisiana, North Carolina, and South Carolina, USA, during 2014–2022. We fitted time to event models to data from radio-marked birds to estimate cause-specific mortality and annual survival. We used band recovery models incorporating both band recovery and telemetry data to further investigate harvest rates and survival. Annual survival from known-fate models in hunted populations was 0.54 (95% CI = 0.49–0.59) for adults and 0.86 (95% CI = 0.81–0.92) for juveniles. Cause-specific mortality analysis produced an annual harvest estimate of 0.29 (95% CI = 0.24–0.33) for adults and 0.02 (95% CI = 0.01–0.03) for juveniles, whereas predation was 0.15 (95% CI = 0.10–0.20) and 0.12 (95% CI = 0.08–0.17), respectively. Annual survival for adult males in a non-hunted population was 0.83 (95% CI = 0.72–0.97). Survival rate was negatively correlated with harvest rate, indicating harvest was an additive mortality source. Annual survival from band recovery models was 0.40 (95% CI = 0.37–0.44) for adults and 0.88 (95% CI = 0.81– 0.93) for juveniles, whereas annual harvest estimates were 0.24 (95% CI = 0.23–0.25) for adults and 0.04 (95% CI = 0.03–0.05) for juveniles. Both models suggested no differences in annual survival across years or among study areas, which included privately owned and public properties. Harvest was an additive mortality source for male wild turkeys, suggesting that managers interested in increasing annual survival of adult males could consider ways of reducing harvest rates.     

Histological examination ofBorrelia burgdorferi infections in unfedIxodes ricinus nymphs

Borrelia burgdorferi, the agent of Lyme borreliosis, is vectored in Europe byIxodes ricinus. In unfed ticks, the spirochaete resides primarily in the midgut, but a low percentage (5.5%; 4/73) of naturally infected ticks may present a systemic infection involving organs such as the salivary glands and central ganglion (Burgdorferet al., 1983). In this study, we examined 79 unfed nymphs collected in two sites in Switzerland (Neuchatel and Aarberg), and 35 unfed nymphs which were fed as uninfected larvae on 3 infectedApodemus sylvaticus mice. Dieterle silver staining was used to visualize the spirochaetes in the ticks. Of the unfed field-collected nymphs, 21/79 (27%) were infected of which 2/21 (10%) had systemic infections. Taking account of the site of collection, we observed that 0/12 ticks from Neuchatel were systemically infected whereas 2/9 (22%) from Aarberg had a disseminated infection. Out of the 35 unfed nymphs examined after an infectious blood meal on rodents, 14 (40%) were infected and 2 (14%) had a disseminated infection. A total of 4/35 (11%) unfed infected nymphs presented a systemic infection which represents a higher percentage than previously described. The presence of spirochaetes in salivary glands of systemically infected ticks before the initiation of feeding may reduce the time delay generally recorded for the tick-borne transmission ofB. burgdorferi.     

Amplification of tick-borne encephalitis virus infection during co-feeding of ticks

Abstract. Following engorgement of Rhipicephalus appendiculatus larvae on guinea-pigs infected with tick-borne encephalitis (TBE) virus, none of the engorged larvae or emergent nymphs contained detectable infectious virus. However, one of twelve pools, each containing three of the unfed nymphs, was positive when screened by polymerase chain reaction (PCR), indicating a low prevalence of TBE virus infection in the unfed nymphs. After engorgement of the nymphs on four uninfected guinea-pigs, 19/24 (79%) fed nymphs from one guinea-pig and 4/25 (16%) fed nymphs from a second guinea-pig were infected; all the ticks examined from the other two guinea-pigs were uninfected. The results suggest that TBE virus was transmitted from a low proportion of infected nymphs (infected as larvae) to uninfected nymphs as they fed together on an uninfected guinea-pig. Such amplification of the initial infection, at the population level, could play an important role in maintaining TBE virus infections in nature, particularly if there is a low level of vertical transmission from one tick generation to the next.     

Visual Evaluation and Recognition of Hosts by the Tick Parasitoid, Ixodiphagus hookeri (Hymenoptera: Encyrtidae)

The role of host size, movement, feeding status, color, and species in the visual host evaluation and recognition behavior of the tick parasitoid, Ixodiphagus hookeri Howard was investigated. Freshly emerged female parasitoids were subjected to a choice bioassay, where the test materials were placed in sealed vials and the vials placed in a Petri dish. When presented with A. variegatum live and mummified nymphs, females examined: larger nymphs significantly longer than smaller nymphs, fed nymphs significantly longer than unfed nymphs, dead and live nymphs for similar lengths of time, and grey live nymphs and yellow-brown and dark brown mummified nymphs for similar lengths of time. The total number of visits to vials containing these test materials were also not significantly different, except there were significantly more visits to yellow-brown mummies when compared to the number of visits to dark brown mummies. When presented with A. variegatum (host) and R. appendiculatus (nonhost) nymphs, the females examined A. variegatum nymphs significantly longer than R. appendiculatus nymphs. The total number of visits to vials containing A. variegatum nymphs were significantly more than the visits to the vials containing R. appendicualtus nymphs. Furthermore, females spent significantly more total examination time per visit on larger and fed A. variegatum nymphs when compared to smaller and unfed nymphs, respectively. Direct and indirect detection were significant when females were presented with fed versus unfed A. variegatum nymphs, grey nymphs versus yellow-brown mummies, and R. appendiculatus versus A. variegatum nymphs. Direct and indirect detection for the rest of the bioassays were not significantly different. Finally, The percentages of females contacting large fed A. variegatum nymphs first were significantly different from those of females contacting small unfed R. appendiculatus nymphs first. The firstcontact percentages for the rest of the bioassays were not significantly different.     

Analysis of stage-specific and shared antigens derived from Rhipicephalus sanguineus by electrophoresis and Western blotting

e carried out an SDS-PAGE analysis of antigens of Rhipicephalus sanguineus using extracts of eggs (EE), larvae (LE), nymphs (NE), male salivary glands (MSGE), male midguts (MME), female salivary glands (FSGE) and female midguts (FME). Under non-reducing conditions a common band of about 205 kDa was observed. EE, LE and NE extracts showed groups of bands between 150 and 75 kDa. A protein pattern was observed in FSGE extract with a group of bands between 75 and 50 kDa and four bands between 15 and 6.5 kDa. In this case an apparently exclusive band of molecular weight about 25 kDa was observed. Under reducing conditions similarities between LE and NE extracts increased, separating from the EE pattern. On the other hand, we have determined the presence of stage-specific and common antigens on EE, LE, NE, MSGE, MME, FSGE and FME extracts of R.sanguineus by means of immunoblots using polyclonal sera of rabbits infested with larvae, nymphs or adults of this tick. EE extract was only recognized by the anti-larva sera. Higher reactivity was observed when the extracts were tested with anti-adult sera. In these experiments a very prominent band of molecular weight about 45 kDa was detected. This band was not observed under reducing conditions. Higher reactivity with anti-adult sera was observed against FSGE extract.     

Use of carbon dioxide and natural or synthetic aggregation-attachment pheromone of the bont tick,Amblyomma hebraeum,to attract and trap unfed adults in the field

It was determined previously that unfed adults ofAmblyomma hebraeum become active in response to carbon dioxide but are not attracted by it. We have now shown in field experiments that males and females which are activated by carbon dioxide are attracted to the aggregation-attachment pheromone produced by males after a period of feeding on the host. Unfed adults were attracted too-nitrophenol, a component of the aggregation-attachment pheromone ofAmblyomma variegatum, pre-fed males ofA. hebraeum, and extracts of such males. Live males were more attractive than the extracts which, in turn, were more attractive thano-nitrophenol. The ticks were attracted to sources ofo-nitrophenol from as far away as 11 m in 90 min. Simple traps, baited with carbon dioxide and aggregation-attachment pheromone (from pre-fed males or extracts of pre-fed males), were used to capture unfed adults that had been released in the field. The response of unfed adults to carbon dioxide and the aggregation-attachment pheromone presents an obvious host-location mechanism and a means for the ticks to discriminate between suitable hosts (those with males already attached) and potentially unsuitable hosts (those with no males attached).     

Lifecycle of Rhipicephalus haemaphysaloides under laboratory conditions

Rhipicephalus haemaphysaloides Supino, 1897 (Ixodida: Ixodidae) is a three‐host hard tick widely distributed in Sri Lanka. The lifecycle of the R. haemaphysaloides population in Sri Lanka was studied under laboratory conditions using fully engorged females collected from dogs. Larvae, nymphs and adults were reared on New Zealand rabbits. Engorged females weighed a mean ± standard deviation (SD) of 470.1 ± 106.5 mg and laid a mean ± SD of 4067.4 ± 3136.2 eggs within 16.1 ± 3.7 days. The mean ± SD preoviposition period was 6.5 ± 1.1 days. The mean ± SD reproductive efficiency index was 8.5 ± 4.1, and was higher in heavier females (Pearson correlation, r = 0.8; P = 0.001). The incubation period of eggs was shorter at higher temperatures. The majority (86.9%) of larvae successfully moulted after a mean ± SD premoulting period of 7.9 ± 0.7 days following a parasitic period of 3.2 ± 0.5 days. Unfed larvae survived a mean ± SD of 103.4 ± 19.8 days. Nymphs completed the bloodmeal after 3.7 ± 0.9 days, weighed 5.7 ± 1.7 mg and demonstrated a premoulting period of 15.1 ± 1.9 days. Unfed nymphs survived a mean ± SD of 45.8 ± 3.8 days. Heavier nymphs moulted into females, whereas lighter nymphs moulted into males (two‐sample t‐test, P < 0.001). The bodyweight of adult females increased more than 100‐fold after feeding. The lifecycle of R. haemaphysaloides was successfully completed on rabbits within a mean of 91.3 days (range: 69–117 days) under laboratory conditions.     

Differences in competitive ability for the occupancy of shelters in triatomines

Triatomines (Hemiptera: Reduviidae: Triatominae) are nocturnal blood‐sucking insects. During daylight hours they remain in an akinetic state inside their shelters, whereas at dusk they become active and move outside. When they are outside their shelters during the photophase, triatomines are vulnerable to diurnal predators and the period just before dawn is critical to their survival. This work analyses the existence of competitive interactions involved in the occupancy of shelters by triatomines. Behavioural assays were performed in which nymphs of different stages, nutritional status or species were released in an experimental arena containing a space‐limited artificial shelter. The proportions of individuals occupying the shelter during the photophase were quantified to estimate the competitive abilities of each stage and species. Intraspecific comparisons showed higher levels of shelter occupancy for fourth over fifth instars and fed over unfed nymphs of Triatoma infestans. Interspecific comparisons showed higher rates of shelter occupancy for Triatoma sordida in comparison with T. infestans, and for T. infestans over Rhodnius prolixus. Arrival order was also relevant to determining shelter occupancy levels: early arrival was advantageous in comparison with later arrival. The study of intra‐ and interspecific competitive interactions for shelter occupancy provides relevant information about colonization and recolonization processes in the natural environments of triatomines.     

Lifestyle factors and incident mobility limitation in obese and non-obese older adults

Objective: This study examines the association between incident mobility limitation and 4 lifestyle factors: smoking, alcohol intake, physical activity, and diet in well‐functioning obese (n = 667) and non‐obese (n = 2027) older adults. Research Methods and Procedures: Data were from men and women, 70 to 79 years of age from Pittsburgh, PA and Memphis, TN, participating in the Health, Aging and Body Composition (Health ABC) study. In addition to individual lifestyle practices, a high‐risk lifestyle score (0 to 4) was calculated indicating the total number of unhealthy lifestyle practices per person. Mobility limitation was defined as reported difficulty walking 1/4 mile or climbing 10 steps during two consecutive semiannual assessments over 6.5 years. Results: In non‐obese older persons, significant risk factors for incident mobility limitation after adjustment for socio‐demographics and health‐related variables were current and former smoking [hazard ratio (HR) = 1.51; 95% confidence interval (CI), 1.20 to 1.89; HR = 1.40; 95% CI, 1.12 to 1.74), former alcohol intake (HR = 1.30; 95% CI, 1.05 to 1.60), low and medium physical activity (HR = 1.78; 95% CI, 1.45 to 2.18; HR = 1.29, 95% CI, 1.07 to 1.54), and eating an unhealthy diet (HR = 1.57; 95% CI, 1.17 to 2.10). In the obese, only low physical activity was associated with a significantly increased risk of mobility limitation (HR = 1.44; 95% CI, 1.08 to 1.92). Having two or more unhealthy lifestyle factors was a strong predictor of mobility limitation in the non‐obese only (HR = 1.98; 95% CI, 1.61 to 2.43). Overall, obese persons had a significantly higher risk of mobility limitation compared with non‐obese persons, independent of lifestyle factors (HR = 1.73; 95% CI, 1.52 to 1.96). Conclusions: These results underscore the importance of a healthy lifestyle for maintaining function among non‐obese older adults. However, a healthy lifestyle cannot overcome the effect of obesity in obese older adults; this stresses the importance of preventing obesity to protect against mobility loss in older persons.     

The water system of traditional rice paddies as an important habitatof the giant water bug, <Emphasis Type="Italic">Lethocerus deyrollei</Emphasis> (Heteroptera: Belostomatidae)

The population dynamics of Lethocerus deyrollei, including the seasonal change in the habitat utilization, were studied in five types of waters, permanent and temporary pools, ditch, rice paddy and marsh in a Satoyama, the traditional landscape in Japan consisting of mixtures of coppice woodlands, farmlands, and settlements, in northern Osaka, from June, 1999 to December, 2001. A mark and recapture census was carried out with adults, and the stage and the number were recorded in nymphs. A total of 95 adults were numbered, and 48 (51%) were recaptured in all the five water types during the study period. Adults of the new generation appeared from late July, and disappeared before the winter in all types of waters. A total of three overwintered adults were recaptured in permanent and temporary pools, ditch, and paddy from between early April and early June. Densities of both L. deyrollei adults and their prey, tadpoles and frogs, were high in permanent and temporary pools, and ditch, in which water temperatures were high in the summer season. Third to fifth (final) instar nymphs were also observed in all water types with different densities in summer, while first and second instars were found only in permanent pool, ditch and paddy habitats in which water temperatures were high and oviposition substrata such as the rice plant, other hygrophytes and wooden stakes existed. These results show that the traditional water system of paddy in the Satoyama landscape as a whole provides an important habitat for L. deyrollei which is now under threat by changing agricultural practices like other native biota inhabiting the system.     

Moulting and survival of <Emphasis Type="Italic">Amblyomma variegatum</Emphasis> (Acari: Ixodidae) nymphs in quasi-natural conditions in Burkina Faso; tick predators as an important limiting factor

The survival rate of Amblyomma variegatum engorged nymphs was studied in 9 cohorts released during the first part of the dry season (i.e. the nymph infestation period in the region) and placed on a natural savannah, either in plastic containers or in cages driven into the soil and open at the bottom. All nymphs put in the containers placed in the sun died rapidly, while a high moulting rate (94%) was observed in containers placed in the shade. This rate reached 63% for the ticks released in the cages. The moulting period lasted from less than 4 to more than 6 weeks, depending on the release period: unfed adults are therefore present in the pasture 4–5 months before the onset of the adult infestation period. The survival rate of the unfed adults did not vary according to the release period of the nymphs: at the beginning of the rainy season, 20–25% of the adult ticks were still alive in the cages. Very important variations in survival and disappearance rates were observed according to the place where the cages had been installed: within a few metres, the survival rate could vary from 0 to 90%, presumably because of the activity of predators which removed also dead tick from the plastic containers. Predators may then have a great but highly variable and unpredictable impact on the natural population of A. variegatum adults. Engorged nymphs released on pasture were able to find suitable micro-habitats allowing survival, covered up to 2.8 metres to reach them, and grouped together at the neck or root network of bushes and grass clumps, sometimes burrowing to a depth of 10 cm.