Host Age Groups Research Articles

Integrative taxonomy of Metastrongylus spp. in wild boars from Brazil

BackgroundWild boars (Sus scrofa) may cause substantial damage to crops and can spread zoonotic parasites to domestic animals, posing a risk to health and animal production. Metastrongylus spp. can negatively affect the wild boar population, increasing piglet mortality. In addition to that, studies with Metastrongylus genetic characterization are still scarce in Brazil. The present study aims to characterize Metastrongylus spp. from wild boars hunted in the states of São Paulo, Paraná, and Rio Grande do Sul, Brazil, using traditional morphological description and DNA sequences in an integrative taxonomic approach.MethodsAfter nematode collection from 58 wild boars, the parasites were morphologically identified and genetically characterized by the amplification of 18S ribosomal DNA (rDNA), 28S rDNA, internal transcribed spacer (ITS) region, and cox-1 mitochondrial DNA (mtDNA). Descriptors of infection were determined and Pearson's Chi-square test was applied to compare the prevalence of infections among the identified parasite species, host age group (juveniles and adults), and sex. The Mann–Whitney U test was performed to compare the mean intensity between the age groups and sex.ResultsMetastrongylus salmi, Metastrongylus apri, and Metastrongylus pudendotectus were identified in 77.6% (45/58) of the necropsied wild boars. Metastrongylus salmi was the most prevalent and abundant species (70.7%, 11.1), followed by M. pudendotectus (18.9%, 4.3) and M. apri (17.2%, 2.2). Metastrongylus pudendotectus showed the highest mean intensity and range (25.2, 1–93), followed by M. salmi (15.7, 1–58) and M. apri (12.6, 3–27). We found a significantly higher prevalence of Metastrongylus spp. and M. salmi in adult wild boars, probably associated with a more prolonged time of exposure to intermediate host species. The phylogenetic analysis revealed that ITS2 region and cox-1 mtDNA are the most suitable genetic markers for Metastrongylus species characterization. Genetic variability between M. apri and M. salmi isolates was verified.ConclusionsWe expand the knowledge about the Metastrongylus community in the non-captive wild boar population from Brazil as well as the importance of this exotic species in the maintenance of Metastrongylus spp. in its areas of occurrence. The novel genetic sequences obtained may help further studies to understand the genetic diversity in other nematode populations from Brazil and other countries.Graphical

Seroprevalence of Fasciola-infection using Enzyme-linked immunosorbent assay in large ruminants from Pakistan

Fasciolosis, caused by liver fluke species of the genus Fasciola, are well recognized because of its high veterinary impact. Stool examination for Fasciola eggs is not a sensitive method, and limited efforts to find a reliable and cheaper means of detection are available. The present study aimed to develop rapid diagnostic ELISA test against fasciolosis. The excretory/secretory (ES) and somatic (SA) products of Fasciola helminths were analysed using polyacrylamide gel electrophoresis (PAGE). Immunogenicity was evaluated by immunoblotting using hyperimmune sera raised in rabbits and seroprevalence was determined by indirect ELISA. The results of SA antigen of Fasciola species showed polypeptide bands ranged from 10kDa-100kDa, while ES antigen of Fasciola showed bands of 15kDa-55kDa. The immunoblotting results showed the most prominent bands against ES antibodies were 25, 35, 55-70, 100 and 250 kDa and SA antigens showed 10, 15-25, 35, 70, 100 and 250 kDa polypeptide bands. The sensitivity and specificity of developed indirect ELISA for SA antigens was 95.45% and 87.1%, while for ES antigens was 100% and 77.42% respectively. The overall seroprevalence recorded for fascioliasis based on SA antigen was 39.8% and 29.8% for ES antigen. The fasciolosis did not show significant association with host type, sex and age groups of examined animals, however significantly higher infection was found in months of September and October. The result provides sensitive in house immunodetection assay for diagnosis of fasciolosis alternative to commercial kits with high import cost.

Non-native Nematode Ashworthius sidemi Currently Dominates the Abomasal Parasite Community of Cervid Hosts in the Czech Republic

Ashworthius sidemi is an abomasal nematode typical for Asiatic cervids such as sambar (Rusa unicolor) or sika deer (Cervus nippon). This non-native parasite was introduced into Europe via sika deer in the late 19th and early 20th centuries. The current dynamic spread of this parasite amongst autochthonous wild cervids occurs independently of human activities, and A. sidemi has a negative impact on the health of wild ruminants and may pose a threat to the conservation of endangered wild ungulates and to livestock. This invasive parasite has been previously detected in the Czech Republic, but more accurate information on A. sidemi is required. Only limited information is generally available on the factors influencing the spread of abomasal nematodes in wild ruminants, so more information is necessary for planning effective strategies of parasite control. We therefore conducted a survey on the abomasal nematodes in cervids in both game reserves and hunting grounds across the Czech Republic, taking into account the hosts (species, age, sex) and environmental factors (monthly average temperature). The abomasa of 104 animals belonging to five cervid species originating from various locations of the country were collected. Data on host (species, sex, and age group) and the monthly average temperature in the region were obtained for each animal. The parasitological analyses indicated that 92% of the abomasa were infected by nematodes. Ashworthius sidemi was the most prevalent (72%) and abundant (80% of the total recovered individuals) nematode species and was detected in all cervid species except white-tailed deer. The intensity of A. sidemi was highest in roe deer (Capreolus capreolus) and fallow deer (Dama dama), but A. sidemi abundance did not depend substantially on the host or environmental factors. In contrast, the abundance of nematodes from the subfamily Ostertagiinae was influenced by the host species and temperature. Parasitic load was significantly higher in roe deer and during the warmer periods of the survey. We also detected another non-native nematode species, Spiculopteragia houdemeri. The results of our study suggest that the non-native nematode A. sidemi is now widespread amongst cervid hosts in the Czech Republic, probably due to the high sensitivity of autochthonous cervids to A. sidemi infections as well as adaptation of this parasite to the current climatic conditions of this country.

Effects of different Philosamia ricini (Lepidoptera: Saturniidae) cold storage periods on Ooencyrtus pityocampae and Ooencyrtus kuvanae (Hymenoptera: Encyrtidae) rearing.

Ooencyrtus pityocampae and Ooencyrtus kuvanae are egg parasitoids that are considered potential candidates for the control of different pest species through inundative release. The aim of this study was to assess the effects of different cold-storage periods of Philosamia ricini eggs (host) on the rearing parameters of O. pityocampae and O. kuvanae. Host eggs were stored at 3 °C, and a factorial experiment involving two parasitoid species, nine host storage periods (1, 5, 10, 15, 30, 45, 60, 75 and 90 days) and a control, and two host ages (1 and 2 days) was conducted, with 10 replications including 40-P. ricini eggs each. Adult emergence, development time, longevity, and fecundity were investigated. The parasitoid adult emergence percentage significantly varied with storage duration. These values were lower in O. kuvanae than in O. pityocampae. The development time of O. kuvanae progeny increased in both host age groups except in the 1-day storage period subgroup. However, the development times of the progeny of O. pityocampae reared on one-day-old eggs stored for 5, 10, 60, and 75 days were increased, and the development times of the progeny of O. pityocampae reared on 2-day-old eggs stored for 45 and 90 days were increased. The longevity of the F1 progeny of O. kuvanae was negatively affected by storage time. There was no difference in the longevity of the F1 progeny of O. pityocampae compared to that of the control. Additionally, the fecundities of the F1 progeny of O. pityocampae and O. kuvanae were 54.7 and 47.0 offspring/female, respectively. These results provide useful information for guiding the development of mass rearing methodologies for both parasitoid species.

Diagnostic potential of 36-55 kDa somatic antigens of Fasciola gigantica for bovine fasciolosis

Fascioliasis causes huge economic losses in livestock industry by reducing the growth, fertility rate, meat and milk yield. In the present study, somatic antigens isolated from Fasciola gigantica were assessed for the early detection of infection by developing antibody detection enzyme immunoassay. The somatic antigens extracted from adult F. gigantica worms was separated on SDS-PAGE and immunogenicity was determined by Western blot (WB). The results showed polypeptides bands between 15 to 95 kDa, and most prominent bands were 15, 28, 36, 38, 55, 72 and 95 kDa polypeptides. The WB revealed a single polypeptide of size between 36 to 55 kDa as antigenic. The sensitivity and specificity of ELISA test established for 36 to 55 kDa somatic antigens was 95.45% (95% CI: 77.16% to 99.88%) and 87.1% (95% CI: 70.17% to 96.37%), respectively. Kappa value revealed that the strength of agreement is considered to be very ‘good’. In house established ELISA was implemented in the field and 12.1% (31/256) large ruminants were found positive, while 4.68% (12/256) with postmortem examination. The fasciolosis did not show significant (P>0.05) association with host type, breed and age groups, while significant (P<0.01) association with host sexes. The result confirmed that in-house established ELISA test had good value for serodiagnosis of fasciolosis in cattle and buffaloes for large scale epidemiological studies.

Escherichia coli urinary tract infections: Host age-related differences in bacterial virulence factors and antimicrobial susceptibility

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are one of the most common outpatient bacterial infections. Although bacterial and host factors are reported to be associated with UTI pathogenesis, little is known about the host age-related differences in bacterial virulence factors and antimicrobial susceptibility. PCRs were carried out to detect K1 capsule antigen, 15 virulence factors, and phylogenetic groups in E. coli isolates. Antimicrobial susceptibility of selected agents was determined by the disk diffusion method. Isolates were divided into 6 groups based on their host age. The results showed that virulence factors PapGII, PapGIII, Cnf1, Aer, Usp, Iha, OmpT, HlyA, and Sat, had highest frequencies in the host age group 0-3. Phylogenetic group B2 dominated in our isolates (59.6%) followed by group D (20.7%). In addition, 77.4% of strains isolated from 0 to 3 age group belonged to phylogenetic group B2. Antimicrobial susceptibility tests showed that E. coli strains isolated were significantly more resistant to antimicrobial agents as host age increased. Phylogenetic group B2 isolates were more susceptible to antimicrobial agents, compared to A, B1, and D isolates. We found E. coli isolated from elders were more resistant to antimicrobial agents and had less virulence factors.

Nemabiome metabarcoding reveals differences between gastrointestinal nematode species infecting co-grazed sheep and goats

Our current understanding of differences in the epidemiology of gastrointestinal nematode (GIN) species in co-grazed sheep and goats is inadequate with reference to the development of sustainable control strategies. The next-generation metabarcoding sequencing method referred to as the ‘nemabiome’ allows some of these differences to be explored to describe the intensity of co-infecting GIN species. We applied this platform to study sheep and goats that were co-grazed on Guinea grass pasture in northeastern Brazil. Co-grazed goats and sheep were treated with a monepantel anthelmintic, then exposed to the same gastrointestinal nematode species. Overall, there were differences in the prevalence of GIN species identified in the sheep and goats; Trichostrongylus colubriformis and Teladorsagia circumcincta predominated in goat kids, while Haemonchus contortus predominated in adult does, ewes and lambs once burdens became re-established after anthelmintic treatment. Description of the pattern of re-infection following anthelmintic treatment was prevented by the unpredicted poor efficacy of 2.5 mg/kg and 5 mg/kg, respectively, of monepantel against O. columbianum and T. circumcincta in lambs, and T. circumcincta adult does. Differences in drug efficacy between host age and species groups may be important when considering sustainable GIN control strategies for co-grazed animals. The aggregated FECs of the adult does and goat kids representing re-established GIN burdens, were higher than those of the co-grazed adult ewes and lambs. This implies that there are inherent differences in GIN species adaptation to the two naïve small ruminant host species, and shows the need for better understanding of the factors giving rise to this situation associated with exposure to infective larvae and host responses. At the start of the study, the adult does were co-infected with several GIN species, with the highest intensity of T. circumcincta, contrasting with the situation in the adult ewes, in which H. contortus predominated. However, once burdens became re-established after treatment, H. contortus predominated in both adult does and ewes. This demonstrates the potential for host burdens of H. contortus to establish and predominate after anthelmintic treatment when burdens of co-infecting GIN species are low.

Performance of the parasitoid species Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday)\xa0(Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), using Myzus persicae (Sulzer) (Hemiptera: Aphididae) as host

Three parasitoid species viz. Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday) (Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) parasitizing the aphid species Myzus persicae (Sulzer) (Hemiptera: Aphididae) in mid-hills of north India were studied. At different locations and times of the year, the parasitization by A. asychis, A. ervi, and D. rapae ranged from 7.53 to 37.58, 4.26 to 80.45, and 74.25 to 80.48%, respectively. All the 3 parasitoids successfully completed their development on different nymphal instars of the aphid host and the total developmental duration of A. asychis, A. ervi, and D. rapae ranged 10.4–14.6, 24.2–29.6, and 10.2–15.2 days, respectively. It was significantly longer on the 1st nymphal instar of the host. The longevity of the female parasitoids was significantly longer than their counterparts. Differences in host age significantly influenced the longevity of female parasitoids and it was more on 1 to 2-day-old nymphs than that on 4 to 5-day-old nymphs. Fecundity and ovipositional periods of the parasitoids on younger (1–2 days old) host age group were considerably prolonged than on the older ages of the aphid. Average total fecundity of A. asychis and D. rapae was significantly higher when parasitizing 1–2-day-old nymphs. In A. asychis, host feeding behavior was also observed by a total host feeding of 89.2 aphids (1–2 days old) and 43.4 aphids (4–5 days old) during its life span. It is concluded that A. asychis, A. ervi, and D. rapae can be mass reared using M. persicae as host and can be utilized successfully in augmentative biological control program.

Dose response models for Eastern US, Western US and Venezuelan equine encephalitis viruses in mice – Part I: Standard dose response model and inference of host age

Data regarding mice exposed to Eastern, Venezuelan and Western equine encephalitis viruses (EEV, VEV and WEV respectively) were used to optimize two physiologically plausible dose response models. A rich data set was extracted from an intensive literature review, with 42 independent dose groups over three exposure routes: subcutaneous, intracranial and intraperitoneal. The data demonstrate the highly infectious nature of these encephalitis viruses to a general population. However, from an examination of the data, a dependency in the dose response relationship with respect to host age is likely. This host age dependency is manifesting as an increased resistance with increased host age, conversely, higher susceptibility at lower host ages. Considering the inability to pool host age groups under a nested model, this likely host age dependency is highlighted to a greater extent. Most of the host age groups (65%) could not be used for dose-response model optimization, leaving 13 host age groups of the original 37 that could be used for optimization. Those that could be used resulted in the exponential model being the better fitting model for 61% of those data, with the approximated form of the beta Poisson being the better fitting model for the remaining five data sets.

Signatures of divergent anti-malarial treatment responses in peripheral blood from adults and young children in Malawi

BackgroundHeterogeneity in the immune response to parasite infection is mediated in part by differences in host genetics, gender, and age group. In infants and young children, ongoing immunological maturation often results in increased susceptibility to infection and variable responses to drug treatment, increasing the risk of complications. Even though significant age-associated effects on host cytokine responses to Plasmodium falciparum infection have been identified, age-associated effects on uncomplicated malaria infection and anti-malarial treatment remain poorly understood.MethodsIn samples of whole blood from a cohort of naturally infected malaria-positive individuals with non-severe falciparum malaria in Malawi (n = 63 total; 34 infants and young children < 2 years old, 29 adults > 18 years old), blood cytokine levels and monocyte and dendritic cell frequencies were assessed at two timepoints: acute infection, and 4 weeks post anti-malarial treatment. The effects of age group, gender, and timepoint were modeled, and the role of these factors on infection and treatment outcomes was evaluated.ResultsRegardless of treatment timepoint, in this population age was significantly associated with overall blood haemoglobin, which was higher in adults, and plasma nitric oxide metabolites, IL-10, and TNF levels, which were higher in young children. There was a significant effect of age on the haemoglobin treatment response, whereby after treatment, levels increased in young children and decreased in adults. Furthermore, there were significant age-associated effects on treatment response for overall parasite load, IFN-γ, and IL-12(p40), and these effects were gender-dependent. Significant age effects on the overall levels and treatment response of myeloid dendritic cell frequencies were observed. In addition, within each age group, results showed continuous age effects on gametocyte levels (Pfs16), TNF, and nitric oxide metabolites.ConclusionsIn a clinical study of young children and adults experiencing natural falciparum malaria infection and receiving anti-malarial treatment, age-associated signatures of infection and treatment responses in peripheral blood were identified. This study describes host markers that may indicate, and potentially contribute to, differential post-treatment outcomes for malaria in young children versus adults.

Faunal diversity and dynamics of species richness and dominance of parasite communities in age series of the perch (Perca fluviatilis)

Changes in parameters of species richness and dominance in parasite communities of perch have been analyzed in the age series of hosts from two water bodies, Lake Gusinoe and Chivyrkui Bay (Lake Baikal), at the levels of a host individual (infracommunity) and a host age group (set of infracommunities). The species richness of parasite infracommunities has been found to increase in both age series due to decreasing proportions of fish affected by no more than three to four parasite species and increasing proportion of fish parasitized by more than four to five species.

Occurrence of phthirapteran ectoparasite parasitizing on domestic dogs, Canis familiaris (Linne) in Jaunpur district (U.P.)

Only two species of biting louse, Heterodoxus spiniger (Enderlein) (43.27%) and Trichodectes canis (De Geer) (13.47%) have been recorded from 245 dogs examined in twelve different localities in Jaunpur district during 2009 to 2011. Female dogs were found most prevalent in comparison to the male in both the cases. Different parameters like host sex, hair colour, hygienic condition, health and age group have been taken into the consideration during the survey. Older age groups, unhealthy and unhygienic condition of dogs were found more prone for the lice. In case of relative intensity of lice 38% were found moderately infested with H. spiniger while 23% and 16% were very light and light infested. Only 12% could be recorded heavy infested dog while 8% remained very heavy infested. Similar trends were recorded for T. canis where moderate infestation followed by very light, light, heavy and very heavy infestation respectively. Besides these two lice, some other ectoparasites (ticks, mites and fleas) (5.31%) were also recorded casually but not used the data for prevalence.

Helminth Community Composition, Structure, and Pattern in Six Dove Species (Columbiformes: Columbidae) of South Texas

The helminth community composition and structure of 6 species of columbids residing in south Texas are reported and compared herein. Sixty individuals of the following species, rock pigeons (Columba livia [RP]), mourning doves (Zenaida macroura [MD]), Eurasian collared-doves (Streptopelia decaocto [ECD]), white-winged doves (Zenaida asiatica [WWD]), and common ground doves (Columbina passerina [CGD]), and 48 Inca doves (Columbina inca [ID]) were collected during the summer of 2006 and examined for helminths. Twelve helminth species were found (9 nematodes and 3 cestodes), representing 486 individuals. Nematodes numerically dominated the component community in all host species. Overall, helminth prevalence was similar among host sex within all dove species. However, prevalence of Skrjabinia bonini and Hymenolepis sp. in RPs was significantly different among host age groups (P = 0.01, P = 0.0002, respectively). Likewise, prevalence of Killigrewia delafondi was higher (P = 0.0001) in adult WWDs. Based on percent similarity and Jaccard's coefficient of community indices, helminth component communities were dissimilar, and the number of shared helminth species varied among host species. Data from this study suggest that the environment surrounding preferred host habitat and foraging strategies of each host species is the driving force behind helminth component communities. This study emphasizes the importance of examining co-occurring hosts at both local and regional scales to elucidate helminth community structure and patterns.

Dependence that the community structure of the roach Rutilus rutilus (L.) parasites has on the host age

The changes that take place in the structure of the parasite communities of two roach populations as the hosts grow older have been studied in the Chivyrkuiskii Bay of Lake Baikal and the estuary of the Selenga River. The parasite communities are analyzed at the levels of host individuals (infracommunities), host age groups (sets of infracommunities), and host population (component community). The number of parasite species regularly increases as the roaches age in both aquatic bodies, whereas the evenness of the parasite communities decreases. The Berger-Parker dominance index of the parasite communities changes with the roach age in different directions, increasing in the Chivyrkuiskii Bay and decreasing in the estuary of the Selenga River. The changes in the Shannon diversity index for sets of infracommunities of roach parasites are the opposite of those in the Berger-Parker index.

Baikal whitefish Coregonus baicalensis Dybowski, 1874 parasite communities and host age

Data on the taxonomic diversity of Baikal whitefish parasites are summarized in the study. Significant correlations of some parasite species' relative abundance and parasite communities' (infracommunities and component communities) parameters with host age were found during the study of parasite distribution in the host's age groups in the Baikal whitefish population from Chivyrkui Bay of Lake Baikal. Study of morphobiological and genetic features which have arisen due to long-term geographic isolation allowed confirming the initial specific independence of lake whitefishes of Lake Baikal as Coregonus baicalensis Dybowski, 1874, i.e., the Baikal whitefish (Sukhanova et al., 2000). The main habitats of this Baikal endemic are Barguzin and Chivyrkui bays, Selenga shallow, and Little Sea strait (Pronin et al., 2007). Local populations from these habitats were previously considered to be independent stocks (Krogius, 1933).

Effects of host density, host age, temperature and gamma irradiation on the mass production of Nesolynx thymus (Hymenoptera: Eulophidae), an endoparasitoid of Uzi fly, Exorista sorbillans (Diptera: Tachinidae)

The Uzifly, Exorista sorbillans Weidemann, is an endoparasitoid of the the silkworm moth, Bombyx mori L., and can impact commercial sericulture. Effects of Uzifly age, density, temperature and gamma radiation (60Co) on the mass-production of the hyperparasitoid Nysolynx thymus (Girault) were investigated. There was a direct relationship between progeny production and an increase in number of host puparia presented, and a significant decline in the number of progeny with increased host-age. Maximum progeny production was obtained by maintaining a 1:5 to 1:8 parasitoid-to-host ratio for all the age groups. Two to 4-day-old host puparia were most suitable for obtaining the maximum progeny production of N. thymus for all the host-densities. The intrinsic rate of increase (r m day−1) increased with the increased host density for all the host-age groups. The values of net reproductive rate (R 0) and gross reproductive rate (GRR) increased for all the density levels and host age groups. On the other hand, the values for the doubling time (D) and finite capacity of increase (λ) gradually decreased with increased host density for all the host age groups. Host density and host-age significantly influenced the sex-ratio of progeny in N. thymus. Higher proportions of females were observed at higher host density levels and for younger host age groups. The progeny production and sex ratio of the parasitoid varied significantly with temperature. The maximum mean number of progeny was recorded at 25°C, while the minimum was at 30°C. The trend of progeny production at different temperatures was on the order 25 > 20 > 30°C. The highest values for the net reproductive rate (R 0) and GRR for the progeny production were recorded at 25°C compared to 20 and 30°C. Both the values for doubling time of capacity (D) and finite capacity (λ) increased with the trend of 25, 30 and 20°C. The highest value for the intrinsic rate of increase (r m day−1) of progeny production was recorded at 25°C, while the lowest value was at 20°C. The sex-ratios were always female-biased at all the temperatures. Temperature had a significant effect on the longevity of adult N. thymus. The longevity of the adults decreased with an increase of temperature for both sexes. The highest rate of parasitism was observed at 20°C followed by 25 and 30°C. More than 95% parasitism was observed at all temperatures. Gamma irradiation significantly increased the progeny production of N. thymus when reared either on early or late irradiated host puparia, particularly in the parental generation, but irradiated early host pupae were more suitable for mass production of N. thymus than the irradiated late pupae. The sex ratio of parasitoids developing from gamma irradiated host pupae varied significantly. Higher proportions of females were observed for all the dose and host-age groups.

Life table of the aphid parasitoid Aphelinus asychis (Walker)(Hymenoptera, Aphelinidae) parasitizing different age groups of Aphis gossypii Glover (Homoptera, Aphididae)

The current laboratory study was designed to evaluate developmental duration, pupal mortality, sex ratio, longevity, fecundity and host feeding behaviour of the aphid parasitoid Aphelinus asychis (Walker) (Hymenoptera, Aphelinidae) parasitizing different age groups of Aphis gossypii Glover (Homoptera, Aphididae) at 25 ± 1°C temperature, 60 ± 10% Rh and a photoperiod of 16:8 h (L:D). The results show that the development from egg to adult was significantly affected by host age. It was completed in 14.5 and 14.4 days in 1–2 day old A. gossypii-nymphs, 13.5 and 13.1 days in 4–5 day old nymphs as well as 12.3 and 12.2 days with adults as host for females and males, respectively. No significant differences of pupal mortality and percentage of females among host age groups were detected. The mean percentage of mortality parasitizing different host age groups varied between 23.6 and 26.8%. The sex ratio (♀♀:♂♂) of A asychis with 1–2 day old A. gossypii-nymphs as host was 1:0.9, with 4–5 day old nymphs 1:0.7 and with adult aphids as host 1:0.9. On the average of 32.8 days females lived slightly longer when parasitizing and host feeding on 1–2 day old aphid nymphs than with 4–5 day old nymphs or adults as host. Females lived significantly longer than males. The fecundity of A. asychis- females was highest parasitizing the first age group (232.3 eggs/♂), followed by adults (44.7 eggs/♂) and by the second age group (21.1 eggs/♂). Highly significant differences were also found in the total number of aphids consumed by host feeding. A. asychis host fed on 161.2 aphids of the first age group, followed by 87.9 aphids of the second age group and 42.7 adult hosts. The present study suggests that short developmental duration, high proportion of females, high longevity, high fecundity and host feeding as well as its preference for younger aphid hosts are properties that make A. asychis an interesting alternative for biological control of the cotton aphid in greenhouses.

RELATIONSHIPS BETWEEN HOST INFECTIVITY TO MOSQUITOES AND ASEXUAL PARASITE DENSITY IN PLASMODIUM FALCIPARUM

We describe a statistical model for the relationship between asexual parasite densities of Plasmodium falciparum and the infectivity of the host to mosquitoes. The model takes into account the delay between asexual parasitemia and infectivity resulting from the time course of gametocytemia. It also allows for the need for the blood meal to contain gametocytes of both sexes if infection is to take place. We show that by fitting this model to data from malariatherapy patients it can explain observed patterns of infectiousness of the human host and is consistent with distributions of gametocyte densities in malariatherapy patients. By integrating this model into an individual-based simulation of human populations exposed to endemic P. falciparum transmission, we are able to predict the contributions of different host age groups to the infectious reservoir. Comparison of model predictions with published estimates of this quantity confirms that infected adults hosts are likely to make a significant contribution to the reservoir of transmission, and points to the need for improved population-based estimates of this age-dependence in infectivity of humans in endemic areas.

Effect of the pupal age of Calliphora erythrocephala (Diptera: Calliphoridae) on the reproductive biology of Melittobia acasta (Walker) (Hymenoptera: Chalcidoidea: Eulophidae)

AbstractA laboratory experiment was conducted to determine the effect of the pupal age of Calliphora erythrocephala (Meigen) on the reproductive biology (in terms of number, size, developmental time and longevity of progeny) of the parasitoid Melittobia acasta Walker. Melittobia acasta females of uniform size were given five C. erythrocephala pupae from one of four experimental age groups: 17–24 h, 24–48 h, 48–72 h and 72–96 h, for parasitization. The mean number of progeny produced from the experimental age groups for a 24 h period were 2, 7.6, 15.6 and 13.6, respectively. The parasitoids preferred hosts that were 48–72 h old. There were no significant differences in the mean development time (18.2 days) and size of progeny (mean head width = 0.38 ± 0.01 mm) produced from the experimental host age groups. The longevity of progeny from the four host age groups varied (range: 4–39 days), with those from the 48–72 h group living longest (mean = 25 days). The F1 females from the 48–72 h group were reproductively more successful than those from the other groups, producing a mean F2 progeny of 912 individuals when compared with 867, 801 and 757 individuals from the 24–48 h, 72–96 h and 17–24 h age groups, respectively. These findings make significant contributions to our knowledge of the breeding and utilization of this parasitoid for the biological control of dipteran flies in pigsties and poultry houses.

Nodular onchocercosis of red deer in central Spain

The presence of nodular onchocercosis was investigated post- mortem in 142 red deer (11 calves, 35 yearlings and 96 adults) shot from February 1998 to January 1999, and July–November 1999 in “Quintos de Mora” (Toledo, central Spain), a game property belonging to the National Wildlife Reserves. Between 6 and 13 animals were analysed monthly by inspection for subcutaneous nodules of Onchocerca spp. Subcutaneous nodules of Onchocerca sp. were detected in 24% of the animals. Anatomical locations for nodules were the back and flanks. Infection ranged from 1 to 29 nodules per animal. Adult worms collected from nodules were identified as O. flexuosa. No apparent seasonal trend was observed either in prevalence or in mean intensity of infection, which fluctuated between 48% (5±8 nodules) in winter 1998 and 5% (1±0 nodules) in summer 1999. Prevalence of infection was significantly higher in adult (30%) than in young animals (9% in calves, 11% in yearlings), although no age effect on intensity was observed. The size of the nodules was measured to evaluate the age of infection. Small (recent) nodules (5–6 mm of diameter) were collected in late spring, summer and fall; medium-sized nodules (12–15 mm) were in second half of summer, fall and winter, and large (mature) nodules (20–25 mm) in fall, winter and part of spring. Significant differences were found among host age groups.