Risk Of Parasitism Research Articles

The influence of malaria control interventions and climate variability on changes in the geographical distribution of parasite prevalence in Kenya between 2015 and 2020

BackgroundThe burden of malaria in Kenya was showing a declining trend, but appears to have reached a plateau in recent years. This study estimated changes in the geographical distribution of malaria parasite risk in the country between the years 2015 and 2020, and quantified the contribution of malaria control interventions and climatic/ environmental factors to these changes.MethodsBayesian geostatistical models were used to analyse the Kenyan 2015 and 2020 Malaria Indicator Survey (MIS) data. Bivariate models were fitted to identify the most important control intervention indicators and climatic/environmental predictors of parasitaemia risk by age groups (6–59 months and 5–14 years). Parasitaemia risk and the number of infected children were predicted over a 1 × 1 km2 grid. The probability of the decline in parasitaemia risk in 2020 compared to 2015 was also evaluated over the gridded surface and factors associated with changes in parasitaemia risk between the two surveys were evaluated.ResultsThere was a significant decline in the coverage of most malaria indicators related to Insecticide Treated Nets (ITN) and Artemisinin Combination Therapies (ACT) interventions. Overall, there was a 31% and 26% reduction in malaria prevalence among children aged < 5 and 5–14 years, respectively. Among younger children, the highest reduction (50%) and increase (41%) were in the low-risk and semi-arid epi zones, respectively; while among older children there was increased risk in both the low-risk (83%) and semi-arid (100%) epi zones. Increase in nightlights and the proportion of individuals using ITNs in 2020 were associated with reduced parasitaemia risk.ConclusionIncreased nightlights and ITN use could have led to the reduction in parasitaemia risk. However, the reduction is heterogeneous and there was increased risk in northern Kenya. Taken together, these results suggest that constant surveillance and re-evaluation of parasite and vector control measures in areas with increased transmission is necessary. The methods used in this analysis can be employed in other settings.

Domesticating the wild through escapees of two iconic mediterranean farmed fish species

Extractive fisheries and marine aquaculture share space and target species. Several regional-scale examples exist of escapees entering wild fisheries landings, yet no study has assessed the influence of aquaculture on landings at an ecosystem scale. We examined the effects of farmed fish escapes on fisheries using FAO data and published escape rates for Gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Seabream landings were significantly correlated with the estimated biomass of escaped seabream entering the wild. There was a similar pattern for seabass until 2005, but the overall relationship between landings and escapes was not significant due to the dramatic drop in catches in recent years. We argue that seabass escapees’ relatively high mortality, lower capturability, and minor ‘leaking’ from farms may obscure their influence on landings. Significant positive fisheries regime shifts were detected for both species, matching the onset of aquaculture in the Mediterranean and the period when escapees from aquaculture surpassed landings. Our results suggest that fish escapes of these two iconic species may mask wild stock overexploitation, confound stock assessments, alter genetic diversity, increase the risk of spreading pathogens and parasites, and compete with wild conspecifics while boosting fisheries landings.

A one health study on phylogenetics and risk of pathogenic intestinal parasites at a ranch in Inner Mongolia

Cryptosporidium, Giardia duodenalis, and Enterocytozoon bieneusi are widespread zoonotic pathogens causing gastrointestinal diseases in humans and various animal species. Inner Mongolia, a major beef production region in China, there is a notable absence of comprehensive research on intestinal parasitism. Thus, timely and comprehensive diagnosis is essential to mitigate disease spread and minimize economic losses in the livestock industry. In this study, we collected fecal samples from cattle and humans, as well as soil and water samples, and all samples were tested for pathogenic intestinal protozoa at the Simmental cattle ranch in Wengniute, Chifeng City, Inner Mongolia. Among the 393 samples tested, 76/371 (20.5 %) cattle, 6/11 (54.5 %) ranch workers, 1/7 (14.3 %) water, and 2/4 (50 %) soil samples were positive. Factors affecting the infection rate of intestinal protozoa were examined. Results showed that the infection rate was higher in June than in January, higher in calves than in adults, and higher in diarrheal calves than in healthy calves. Additionally, the infection rate of intestinal protozoa was higher in pathogen-contaminated water source sheds than in uncontaminated sheds. Genetic and evolutionary analyses revealed that the prevalent E. bieneusi subtypes are predominantly J, I, and BEB4, while the G. duodenalis subtypes are assemblages B and E. The Cryptosporidium species identified were C. bovis, C. andersoni, C. parvum, C. ryanae, and C. suis, with C. parvum being a notable zoonotic pathogen. The pathogen sequences from humans, cattle, water, and soil showed 99–100 % similarity, suggesting possible transmission or contamination between animals and the environment. This study contributes to the One Health approach by addressing the gap in research on intestinal protozoa in Inner Mongolia. It provides important data for other ranches in the region to understand the prevalence of such pathogens and develop effective control measures. Using the concept of One Health to analyze the spatiotemporal distribution of intestinal protozoa in pastures is of great significance for maintaining public health.

Survey of the invasive alien pink salmon (Oncorhynchus gorbuscha) for infective agents in the Fennoscandian Rivers Tana and Neiden

Pink salmon (Oncorhynchus gorbuscha, Walbaum 1792) is an invasive alien species in the Fennoscandian rivers, and its growing populations cause concern for their impact on the native salmonids and river ecosystems. One of the major concerns is fish diseases and the potential ability of pink salmon to transmit pathogens to the native salmonid species. In this study, pink salmon were sampled during their spawning migration in the Rivers Tana and Neiden in northern Norway and Finland in 2021. The fish were surveyed for viral hemorrhagic septicemia virus (VHSV), infectious pancreatic necrosis virus (IPNV), infectious salmon anemia virus (ISAV), salmonid alphavirus (SAV), piscine orthoreovirus (PRV), Renibacterium salmoninarum, and Gyrodactylus salaris. No viral diseases or infections with R. salmoninarum or G. salaris were detected. However, 23 % of the fish were found infected with a parasitic roundworm, Hysterothylacium aduncum. Additionally, external anomalies, such as hemorrhages or lesions in the skin, were observed in 35 % of the fish studied, and some of the fish exhibited degenerative myopathy. Based on this study, pink salmon appears not to pose a high infection risk to the native salmonid fish populations in the Rivers Tana and Neiden. Nevertheless, the results demonstrate that pink salmon have the potential to carry salmonid pathogens. More information on the susceptibility of pink salmon to different pathogens and on the overall effect this invasive species has on native fish species is needed. As the number of migrating pink salmon in the Fennoscandian rivers appears to increase, the potential risk of parasites and other pathogens spreading between fish species will also rise.

Gross to gourmet: A social media analysis of Naked Clams as a sustainable delicacy

AbstractAmidst a global food crisis, securing sustainable food sources is vital. Bivalves such as Naked Clams, historically known as shipworms, offer a promising solution due to their low environmental impact, high nutritional value, and rapid growth rates. Contrary to their image as pests, Naked Clams are the fastest growing bivalves and have various health benefits. Believed to be the world's first aquaculture species, cultivated by Aboriginal Australians 8000 years ago, they are a delicacy in Southeast Asia. Public perception of Naked Clams remains largely unexplored, hindered by their association as pests and worm‐like appearance. This study assesses the perception of Naked Clams through social media, analyzing 40 posts across Facebook, Instagram, TikTok, and YouTube, with millions of views and likes. Analysis of nearly 8000 comments revealed that public perception was split, though generally more positive than negative. Concerns included appearance, potential religious dietary conflicts, and the risk of parasites, which can be addressed with educational campaigns. Importantly, 84% of commenters who tried Naked Clams reported liking them. Naked Clams are noted for their high protein content, nutrient density, and health benefits, and are enjoyed in diverse culinary forms, from traditional raw dishes, to battered calamari‐style street foods, to innovative recipes like Naked Clam ice cream. This study highlights the untapped potential of Naked Clams in global diets and calls for further exploration into moving Naked Clams from “gross to gourmet.”

Gender and sex differences in occupation-specific infectious diseases: a systematic review

Occupational infectious disease risks between men and women have often been attributed to the gendered distribution of the labour force, with limited comparative research on occupation-specific infectious disease risks. The...

Prevalence of intestinal parasites in humans and domestic animals in Jirel community, Dolakha, Nepal.

Gastrointestinal (GI) parasites are major health concerns in both humans and domestic animals. Livestock farming is one of the common livelihood practices in rural Nepal. The proximity at human and domestic animal interface increases the chances of dissemination of enteric parasites, especially those of zoonotic importance. This study was aimed at finding the parasite prevalence and risk factors in both humans and their domestic animals in Jirel community. A field survey was conducted on the Jirel ethnic people and their domestic animals in Dolakha district, where a total of 152 fresh fecal samples from humans and domestic animals (cow, pigs, goats, chickens, ducks, and pigeons) were collected. The feces were examined by wet mounts and concentration techniques. A structured questionnaire survey was carried out among the local people and owners of the domestic animals to gather sociodemographic information, awareness, and hygienic practices in relation to parasite transmission. The enteric parasite prevalence was found to be highest in goats (80.0%;12/15), followed by pigs (55.55%;5/9), cows (45.45%;6/11), chickens (11.7%;4/34), and humans (1.41%;1/71), while the fecal samples of ducks and pigeons did not contain any parasites. The only parasite identified in humans was Ascaris lumbricoides. Similarly, three genera of GI parasites (Eimeria sp., Strongyloides sp, and Trichuris sp.) from goats, two genera each from cow (Eimeria sp. and Strongyloides sp.), pigs (Entamoeba sp. and A. suum), and chickens (Eimeria sp. and Ascaridia galli), were detected. Based on the direct field observation, questionnaire survey and laboratory analysis, it is concluded that the Jirel community people are aware of health and hygiene; however, intervention measures are necessary to prevent parasitic infection in their domestic animals.

Risk for Endoparasites Among Production Stages of Female Goats With Notes on Sustainable Parasite Control For Smallholder Flocks

The risk of parasitism in different groups of small ruminants depends on intrinsic, environmental, and management factors. Although there are different views regarding the sex-related risk of endoparasites in small ruminants, females are undoubtedly the most affected group in the flock. Moreover, whether the greater sex-specific risk of parasitic infection observed in female goats in field situations is associated with their production or other intrinsic factors is still under scrutiny. In this paper, cross-sectional epidemiological data collected from selected small ruminant flocks were analysed to determine the distribution, risk, and burden of endoparasites in young, nonpregnant, pregnant, and lactating female goats. There was a higher incidence of gastrointestinal parasites (88.4%, 95%CI= 83.01-92.19) than blood protozoa (54.0%, 95%CI= 46.85-60.92), with a significant difference among the groups. A higher risk of gastrointestinal parasites was observed in lactating (OR = 46.667, P = 0.001) and pregnant (OR = 9.167, P = 0.003) groups. A greater risk of blood protozoan infection was also observed in the pregnant (OR = 5.971, P = 0.0104) and lactating (OR = 3.600, P = 0.0528) groups. A significant increase in the mean faecal egg count of the lactating (2.72 ± 0.76) and pregnant (2.34 ± 0.97) groups (P &lt; 0.05) was accompanied by a significantly lower mean PCV in the lactating group (23.48 ± 4.838) than the kids (29.44 ± 6.13), or nonpregnant (27.80 ± 5.525) groups (P &lt; 0.05). Thus, the pregnant and lactating female goats may experience a greater exposure risk and burden of endoparasites. Therefore, female goats may be selectively targeted for implementing nutritional management, controlled grazing, and selective anthelmintic treatment during pregnancy and lactation to save cost and minimise excessive use of anthelmintic.

Animal Behaviour Packs a Punch: From Parasitism to Production, Pollution and Prevention in Grazing Livestock.

Behaviour is often the fundamental driver of disease transmission, where behaviours of individuals can be seen to scale up to epidemiological patterns seen at the population level. Here we focus on animal behaviour, and its role in parasite transmission to track its knock-on consequences for parasitism, production and pollution. Livestock face a nutrition versus parasitism trade-off in grazing environments where faeces creates both a nutritional benefit, fertilizing the surrounding sward, but also a parasite risk from infective nematode larvae contaminating the sward. The grazing decisions of ruminants depend on the perceived costs and benefits of the trade-off, which depend on the variations in both environmental (e.g., amounts of faeces) and animal factors (e.g., physiological state). Such grazing decisions determine the intake of both nutrients and parasites, affecting livestock growth rates and production efficiency. This impacts on the greenhouse gas costs of ruminant livestock production via two main mechanisms: (1) slower growth results in longer durations on-farm and (2) parasitised animals produce more methane per unit food intake. However, the sensitivity of behaviour to host parasite state offers opportunities for early detection of parasitism and control. Remote monitoring technology such as accelerometers can detect parasite-induced sickness behaviours soon after exposure, before impacts on growth, and thus may be used for targeting individuals for early treatment. We conclude that livestock host x parasite interactions are at the centre of the global challenges of food security and climate change, and that understanding livestock behaviour can contribute to solving both.

How accurate is your average? Considering error when counting sea lice on open-pen salmon farms

Open-net finfish farms require monitoring to manage fish welfare and to mitigate risk for diseases and parasites which could threaten wild fish populations. In salmonid farming the ectoparasite copepod sea lice Lepeophtheirus salmonis (Caligidae) is a major concern. This paper's novel contribution is the application of sampling statistics to determine the number of sea lice which should be sampled per pen so as to report the abundance of sea lice with a given accuracy. It does so considering the different statistical distributions which occur at high- and low prevalence of sea lice and combines these considerations to guide the reader towards counting a number of sea lice which would be more inline with other statistical applications. Existing pen sampling routines are analysed and the sampling error is quantified. These findings need to be taken into account when sampling protocols for sea lice are designed as it is especially important for fish welfare.

Pet travellers' unwanted companions: a parasitic voyage across Europe

In the modern world, country borders do not represent boundaries for the transmission of pathogens. This is also true for parasites that may travel with animals, particularly pets. Dogs and cats are moving across countries more than ever before as a result of adoption, commerce and travels with owners. In addition, climate change supports the establishment of parasites, particularly those transmitted by invertebrate intermediate hosts and vectors, into areas which were previously considered non-enzootic. Therefore, it is important for veterinarians to keep a vigilant eye on such parasitic infections in dogs and cats, be able to recognise compatible signs and feel confident in ordering specific diagnostic tests. This article presents parasites prevalently reported as imported from one European country to another. Furthermore, common clinical manifestations and diagnostic tests are summarised and the preventive measures that should be advised to pet owners are discussed. Raising awareness among veterinary practitioners and pet owners about the risk of parasites spreading in new areas is imperative for controlling and delaying globalisation of important, and potentially lethal, parasitic diseases.

Mosquitoes do not influence Cotton Mouse (Peromyscus gossypinus) giving-up densities

Abstract It is commonly recognized that predation and the risk of predation can have profound effects on behaviors and population ecology of prey. Comparatively, little attention has been paid to the trade-offs hosts make to manage the risk of parasitism, but there is evidence that hosts make behavioral trade-offs to avoid parasitism in ways that resemble those made by prey animals under the risk of predation. Mosquitoes are common hematophagous ectoparasites which parasitize a wide range of vertebrates, resulting in blood loss, distraction, and disease transmission. Many hosts engage in defensive behaviors to repel or kill mosquitoes and these behaviors likely come at the expense of activities such as foraging and vigilance for predators. We placed a mosquito attractant (BG-Sweetscent) and repellant (allethrin) near artificial foraging patches in areas where mosquitoes were common and measured the amount of grain left after a night of foraging (giving-up density) to investigate whether mosquitoes influenced Cotton Mouse (Peromyscus gossypinus) foraging. We predicted that in patches with mosquito attractants, mosquito harassment would cause mice to engage in defensive behaviors which would distract or deter them from foraging, resulting in less grain consumption relative to control patches. Conversely, we predicted that in mosquito-repellent patches, mice would experience less harassment, resulting in more grain consumption. Indoor arena trials found no evidence that the mosquito treatments influenced cotton mouse behavior in the absence of mosquitoes. However, we found no evidence that mosquito treatments affected giving-up densities.

Awareness of parasitic zoonotic diseases among pet owners in Cairo, Egypt

Egyptians are becoming more interested in owning and raising pets; however, most of them lack essential awareness about the risk of zoonotic parasites that could be transmitted. The objective of the present investigation was to evaluate the degree of awareness Egyptian pet owners possess concerning zoonotic parasitic diseases, the risk of transmission, and preventative measures. A cross-sectional study was conducted using an e-survey. Among 246 pet owners, 64.2% (158) were females, and 67.9% (167) belonged to the 20–30 age group. The majority, 78.9% (194), were raising cats. Only 13.8% (34) visited the veterinarian regularly, with significantly higher results among dog owners (p < 0.05). Only 31.3% (77) participants were regularly deworming their pets, and 19.9% (49) were giving their pets prophylaxis against ectoparasites, with significantly higher results among those who visited the veterinarian regularly (p < 0.0001) and among dog owners (p < 0.05). Only 54.1% (133) had heard about the term “zoonoses” before, and about 8.9% (22) of participants showed a history of zoonotic parasitic diseases, with significantly higher results among those who allowed their animals to play with other animals of neighbors and friends (p < 0.05). The obtained results concluded that the surveyed group had a relatively good degree of knowledge regarding pets as a source of zoonotic illness; raising pet owners' awareness regarding the importance of routine medical examinations and minimizing the contact of pets with other stray animals is essential.

Opening a can of worms: Archived canned fish fillets reveal 40 years of change in parasite burden for four Alaskan salmon species.

How has parasitism changed for Alaskan salmon over the past several decades? Parasitological assessments of salmon are inconsistent across time, and though parasite data are sometimes noted when processing fillets for the market, those data are not retained for more than a few years. The landscape of parasite risk is changing for salmon, and long-term data are needed to quantify this change. Parasitic nematodes of the family Anisakidae (anisakids) use salmonid fishes as intermediate or paratenic hosts in life cycles that terminate in marine mammal definitive hosts. Alaskan marine mammals have been protected since the 1970s, and as populations recover, the density of definitive hosts in this region has increased. To assess whether the anisakid burden has changed in salmonids over time, we used a novel data source: salmon that were caught, canned, and thermally processed for human consumption in Alaska, USA. We examined canned fillets of chum (Oncorhynchus keta, n = 42), coho (Oncorhynchus kisutch, n = 22), pink (Oncorhynchus gorbuscha, n = 62), and sockeye salmon (Oncorhynchus nerka, n = 52) processed between 1979 and 2019. We dissected each fillet and quantified the number of worms per gram of salmon tissue. Anisakid burden increased over time in chum and pink salmon, but there was no change in sockeye or coho salmon. This difference may be due to differences in the prey preferences of each species, or to differences in the parasite species detected across hosts. Canned fish serve as a window into the past, providing information that would otherwise be lost, including information on changes over time in the parasite burden of commercially, culturally, and ecologically important fish species.

Anemia among dogs within Maiduguri, Northeastern Nigeria; A Retrospective Approach

Anemia causes morbidity and mortality in dogs and it is one of the signs of disease in this species. Anemia can occur because of decrease or defective production of red blood cells, acute or chronic blood loss or due to intravascular hemolysis, extravascular hemolysis or both. The records of dogs presented for routine checkup at the Veterinary Teaching Hospital, University of Maiduguri was evaluated from 2015-2021 for diagnosed cases of anemia based on routine hematology. A total of 73 dog files were sorted out from the records. Fifty-three (53) dogs were found to be anemic (72.6%), while 20 (27.4%) were non-anemic. Puppies tend to have the microcytic hypochromic anemia possibly due to iron deficiency, while adult dogs had the macrocytic normochromic anemia. Anemia was more prevalent in male dogs than female dogs, probably due to movement of the males during mating season, thereby exposing them to risks of ecto and endo parasitism. In conclusion anemia is prevalent amongst dogs in Maiduguri metropolis, hence there is a need for further studies to identify and characterize the possible etiologies.

Anemia among dogs within Maiduguri, Northeastern Nigeria; A Retrospective Approach

Anemia causes morbidity and mortality in dogs and it is one of the signs of disease in this species. Anemia can occur because of decrease or defective production of red blood cells, acute or chronic blood loss or due to intravascular hemolysis, extravascular hemolysis or both. The records of dogs presented for routine checkup at the Veterinary Teaching Hospital, University of Maiduguri was evaluated from 2015-2021 for diagnosed cases of anemia based on routine hematology. A total of 73 dog files were sorted out from the records. Fifty-three (53) dogs were found to be anemic (72.6%), while 20 (27.4%) were non-anemic. Puppies tend to have the microcytic hypochromic anemia possibly due to iron deficiency, while adult dogs had the macrocytic normochromic anemia. Anemia was more prevalent in male dogs than female dogs, probably due to movement of the males during mating season, thereby exposing them to risks of ecto and endo parasitism. In conclusion anemia is prevalent amongst dogs in Maiduguri metropolis, hence there is a need for further studies to identify and characterize the possible etiologies.

Meta‐analysis suggests that, for marine mammals, the risk of parasitism by anisakids changed between 1978 and 2015

AbstractAs gastrointestinal parasites affect the health of marine mammal species, they are a potentially consequential stressor. Although they are infrequently identified as a cause of mortality, gastrointestinal parasites could drive cryptic declines in individual fitness—including declines in nutritional status—by acting synergistically with other stressors. Nematodes in the family Anisakidae are ubiquitous throughout the world's oceans and are transmitted to marine mammal hosts through the consumption of fish and cephalopod prey. We sought to assess whether marine mammals face a rising risk of gastrointestinal infection due to an increase in anisakid burden of their prey species. We used data compiled from a recent meta‐analysis of anisakid abundance in fish and invertebrates from 1967 to 2015. We reviewed the diets of 113 marine mammal species to identify their known prey species. We extracted data on anisakid burden for each of the prey species and tested whether anisakid abundance in these intermediate hosts had increased over time. Our findings suggest that Anisakis spp. abundance has increased over the past half‐century, while Pseudoterranova spp. burden showed no significant change. Our findings suggest that the risk of Anisakis spp. infection is increasing for marine mammal hosts.

Pesticide hazard, floral resource availability and natural enemies interactively drive the fitness of bee species depending on their crop fidelity

Pesticides, loss of floral resources and parasitism are considered drivers of wild bee decline in agroecosystems, but their interactions are poorly understood under field conditions. Negative impacts are predicted to vary across species of distinct crop fidelity because of the associated consequences for pesticide exposure and dependence on wild flowers. We experimentally established populations of two solitary bee species in apple orchards with distinct pesticide hazard and flower availability in surrounding landscapes. The number of nesting females, their reproduction and offspring survival and parasitism rate were tracked throughout apple bloom. We show that in the solitary bee Osmia cornuta, which showed a strong preference to forage in apple orchards, the number of females remaining at nesting sites towards the end of apple bloom and the overall reproductive success of the released bees declined with pesticide hazard. In contrast, the closely related Osmia bicornis, which showed a lower preference for apple, was not affected by pesticide use in orchards. Floral resource distribution furthermore modulated parasitism rates in both species: while large amounts of locally available resources reduced offspring parasitism, it increased with relatively higher food availability in the landscapes surrounding focal orchards, probably due to the bees foraging on a larger scale and thus longer periods during which nests remained unattended. Our findings provide novel insights into the complex interplay of pesticide exposure, flower availability and parasitism risk driving population dynamics of bees in agroecosystems. They show that in particular the most reliable crop pollinator species are especially harmed by high pesticide use in crops. Our study underpins the key role of reducing pesticide risks for pollinators through effective regulation of potentially hazardous agrochemicals and the promotion of alternative pest regulation approaches along with conserving and restoring flower-rich habitats to sustain pollinator populations in agroecosystems.

Fish feed composition by high-throughput sequencing analysis: Parasite risk assessment

The use of wild small fish species as feed for aquaculture has clearly an economic incentive by speeding the growth of farmed species. Since feed ingredients are sourced from wild fisheries the farmed species could contain natural contaminants which may introduce food safety concerns. In this study, we used High-Throughput Sequencing (HTS) to explore the whole DNA profile of ten dry commercial feeds commonly used by Spanish fish farming companies. The feeds were mainly made of species within the genus Sprattus, Ammodytes and Clupea, and vegetables of the genus Triticum. In the feeds, DNA sequences of parasitic nematodes of fishes (˂1 % total OTUs) were also identified. A taxonomic assignment of query sequences, using a phylogeny-based approach, estimation of pairwise nucleotide identities within and between sequence groups and haplotype network analysis, allow assign short query sequences to the species Phocanema krabbei (Anisakidae) and Hysterothylacium aduncum (Rhaphidascarididae). Both species were identified as ingredient in two and six fish feeds, respectively. This result is of highly concern regarding dietetic recommendations to sensitized patients to anisakids, considering the growing evidence on the possible allergenic potential of both genera, and the recent data on the transfer of anisakid heat-resistant allergens from fishmeal to farm and aquaculture animals.

Host‐dependent larval migration and parasitism risk in a polyphagous moth

AbstractFemale herbivorous insects are expected to oviposit on the host plant providing the best performance of the offspring. However, in some insects the larvae are mobile and are not totally dependent on the mother's choice. They can change host plant when conditions for development or exposure to natural enemies vary between individual plants within a patch. Here we study larval migration and preference between two host plants, cotton and alfalfa, in the Egyptian leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Previous studies have shown that although larval performance is better on cotton, females prefer to oviposit on alfalfa, and this preference corresponds to a higher survival of the eggs. In this study, S. littoralis larvae showed directed movement between host plants and were found to prefer alfalfa over cotton in field test in Egypt, as well as in laboratory selection of feeding site assays. To determine effects by natural enemies, the parasitism rates and various life‐history traits were measured for one larval parasitoid, Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), on several host plants including cotton and clover (equivalent host plant to alfalfa). Overall, parasitism was higher on cotton and parasitoid performance (cocoon mass, adult longevity, and female egg load) was better on cotton compared to clover. This fact suggests an enemy‐free space on clover and alfalfa, as parasitism rate is higher on cotton, and the parasitoid performance is also better on cotton‐fed larvae.