Parasite Strategies Research Articles

Expanding the evidence for cross-species viral transmission from trophic interactions of parasitoid wasps and their hosts.

Parasitoid wasps act as natural biological control agents for several harmful insect species. However, there is a lack of information regarding the exogenous RNA viruses that infect parasitoids and may contribute to the success of their parasitism strategies. This study aimed to investigate the presence, abundance, and replication of known exogenous viruses in two parasitoid wasp species and their corresponding preys. Utilizing publicly available RNAdeep-sequencing data, two previously validated viruses from the parasitoid Tetrastichus brontispae were assessed in the target beetles Brontispa longissima and Octodonta nipae from the same geographic region. This study revealed the presence of the iflavirus TbRV-3 in both T. brontispae and O. nipae-derived samples, suggesting a potential exchange of the virus between the parasitoid and its host. In addition, there is substantial evidence that the Halyomorpha halys virus infects the parasitoid Telenomus podisi. Thus, this study proposes a close evolutionary relationship between the HhV strain identified in the parasitoid Telenomus podisi and the original strain detected in the prey H. halys. The viral association between trophically related species, such as parasitoids and their hosts, is demonstrated using features such as abundance and the presence of double-stranded RNA, which serves as a proxy for virus replication. Therefore, RNA viruses may coexist at both trophic levels, conferring an evolutionary advantage to the parasitism strategy.

On multiple infections by parasites with complex life cycles

Host manipulation is a common strategy of parasites with complex life cycles. It directly affects predator–prey dynamics in trophically transmitted parasites. Theoretical studies suggest that predation‐enhancing manipulation often decimates the prey population, making parasites prone to extinction. Host manipulation, however, can also reduce predation due to conflicting interests when multiple parasites infect a host, which is often neglected in theoretical studies. Misaligned interests of coinfecting parasites can occur due to limited carrying capacity or parasitoid developmental stage. Including this realistic complexity in a mathematical model, the results depart from previous studies substantially. We show that coinfecting multi‐trophic parasites can preserve the predator–prey system and themselves through manipulation and reproduction parameters. Our study highlights the necessity of and provides the means for incorporating the reality of multiple parasites and their multi‐trophic life cycles into the theory of parasite ecology.

Evidence for the importance of trophically transmitted parasites and predation at the lower latitudes of species ranges.

The lack of information concerning how parasitism maps onto host geographical distributions represents a striking gap in ecological knowledge. This knowledge gap limits our understanding of a wide range of phenomena, including the consequences of climate change-induced range shifts of both hosts and parasites. To help solve this problem, we created a predictive theoretical framework and quantified latitudinal variation in parasitism by animal and protozoan parasites throughout the entire contiguous geographical ranges of four estuarine fish species. To circumvent frequent limitations in data and to permit revealing of novel biogeographical patterns, we (i) quantified parasitism at the individual host level, (ii) quantified parasite species diversity and biomass load, and (iii) tracked functionally distinct parasitic consumer strategies. Parasite diversity always increased at lower latitudes, and this pattern was largely driven by parasites using trophic transmission. Furthermore, in three of four cases, the role of fish as predator- versus prey-host for trophically transmitted parasite (TTP) species increased at lower latitudes. Parasite diversity patterns followed predictions more consistently than did biomass load, indicating that increased predation at lower latitudes may decrease observed parasite biomass load. These findings suggest a particularly strong role for TTPs and predation in community structure and dynamics at lower latitudes.

Invasion of the four kingdoms: the parasite journey across plant and non‐plant hosts

ABSTRACTParasites have a rich and long natural history among biological entities, and it has been suggested that parasites are one of the most significant factors in the evolution of their hosts. However, it has been emphasized less frequently how co‐evolution has undoubtedly also shaped the paths of parasites. It may seem safe to assume that specific differences among the array of potential hosts for particular parasites have restricted and diversified their evolutionary pathways and strategies for survival. Nevertheless, if one looks closely enough at host and parasite, one finds commonalities, both in terms of host defences and parasite strategies to out‐manoeuvre them. While such analyses have been the source of numerous reviews, they are generally limited to interactions between, at most, one kingdom of parasite with two kingdoms of host (e.g. similarities in animal and plant host responses against fungi). With the aim of extending this view, we herein critically evaluate the similarities and differences across all four eukaryotic host kingdoms (plants, animals, fungi, and protists) and their parasites. In doing so, we show that hosts tend to share common strategies for defence, including both physical and behavioural barriers, and highly evolved immune responses, in particular innate immunity. Parasites have, similarly, evolved convergent strategies to counter these defences, including mechanisms of active penetration, and evading the host's innate and/or adaptive immune responses. Moreover, just as hosts have evolved behaviours to avoid parasites, many parasites have adaptations to manipulate host phenotype, physiologically, reproductively, and in terms of behaviour. Many of these strategies overlap in the host and parasite, even across wide phylogenetic expanses. That said, specific differences in host physiology and immune responses often necessitate different adaptations for parasites exploiting fundamentally different hosts. Taken together, this review facilitates hypothesis‐driven investigations of parasite–host interactions that transcend the traditional kingdom‐based research fields.

The first record of hyperparasitism in mermithid nematodes

Summary The Mermithidae are primarily simple parasitoids of insects. In this study, we report the first observation of hyperparasitism by mermithid nematodes. Two Mermithidae individuals emerged from a specimen of the parasitoid wasp Coleocentrus incertus collected in Hokkaido, Japan. Although the nematodes were in the juvenile stage and many morphological characteristics were underdeveloped, we were able to observe cross fibre layers on the cuticles. A molecular sequence analysis of the 18S ribosomal DNA suggested that the nematode belonged to the genus Hexamermis, which was supported by the presence of the cross fibre layers. The phylogenetic analysis also suggested a close relationship between our specimens and ‘Mermithidae sp. NM1’, a taxon found in bumblebees, as differences between the sequences of the two taxa were minimal; however, further research is required to confirm the species’ identity. Hyperparasitism by nematodes is rare and is typically unsuccessful in non-host species, yet the nematodes in this study successfully parasitised a parasitoid wasp. Our study is the first to demonstrate that mermithid nematodes can exhibit hyperparasitism in addition to their known parasitic behaviour. The parasitic strategies of Mermithidae nematodes appear to be more flexible than previously assumed, indicating a high degree of adaptability as parasites.

The early dodder gets the host: decoding the coiling patterns of Cuscuta campestris with automated image processing.

We developed an in-house Python-based image analysis pipeline to investigate the movement patterns of Cuscuta. Our analysis unveiled that the coiling and circumnutation movements of Cuscuta are regulated by its intrinsic circadian rhythm. Cuscuta spp., commonly known as dodders, are rootless and leafless stem parasitic plants. Upon germination, Cuscuta starts rotating immediately in a counterclockwise direction (circumnutation) to locate a host plant, creating a seamless vascular connection to steal water and nutrients from its host. In this study, our aim was to elucidate the dynamics of the coiling patterns of Cuscuta, which is an essential step for successful parasitism. Using time-lapse photography, we recorded the circumnutation and coiling movements of C. campestris at different inoculation times on non-living hosts. Subsequent image analyses were facilitated through an in-house Python-based image processing pipeline to detect coiling locations, angles, initiation and completion times, and duration of coiling stages in between. The study revealed that the coiling efficacy of C. campestris varied with the inoculation time of day, showing higher success and faster initiation in morning than in evening. These observations suggest that Cuscuta, despite lacking leaves and a developed chloroplast, can discern photoperiod changes, significantly determining its parasitic efficiency. The automated image analysis results confirmed the reliability of our Python pipeline by aligning closely with manual annotations. This study provides significant insights into the parasitic strategies of C. campestris and demonstrates the potential of integrating computational image analysis in plant biology for exploring complex plant behaviors. Furthermore, this method provides an efficient tool for investigating plant movement dynamics, laying the foundation for future studies on mitigating the economic impacts of parasitic plants.

Use of the Micro-Agar Larval Development Test to Differentiate Resistant and Susceptible Cooperia spp. Isolates in Cattle Within the Context of Parasite Population Replacement.

Gastrointestinal nematode infections are a global concern in grazing cattle production systems, even more so due to the widespread problem of anthelmintic resistance. In response, early anthelmintic resistance detection methods, such as the micro-agar larval development test (MALDT), and parasite management strategies, such as the replacement of resistant parasite populations with susceptible ones, have been developed. This study aimed to characterize ivermectin-susceptible and -resistant isolates of Cooperia spp. using MALDT in the context of a parasite population replacement strategy. Three Cooperia spp. field isolates were evaluated: a susceptible one (Coop-S), a resistant one (Coop-R), and a post-replacement one (Coop-PR). The MALDT was performed in 96-well plates with 12 known concentrations of eprinomectin (EPR) on an agar base. Each test was performed in quadruplicate. Data analysis included nonlinear regression to determine EC50, EC90, and EC99 values, resistance ratios (RRs), and R2. The results showed clear differentiation between the isolates, with RR values of 5.78 and 1.28 for Coop-R and Coop-PR, respectively, compared to Coop-S. The MALDT proved to be a reliable tool for differentiating ivermectin-susceptible from ivermectin-resistant isolates of Cooperia spp., and future evaluations of this test in mixed nematode populations are recommended for routine diagnosis of anthelmintic resistance.

Prevalence and Associated Risk Factors of Helminth Infections in the Digestive Tract of Camels in Xinjiang, China.

Camels, vital to economies in Asia, Africa, and the Arabian Peninsula, have been domesticated for over 4000 years. They thrive in arid regions like Xinjiang, China, but face challenges from internal and external parasites, particularly gastrointestinal parasites, which impact health, meat and milk quality, and production efficiency. This study investigates the prevalence of gastrointestinal helminth infections in camels from five major regions in Xinjiang. We collected 435 fresh fecal samples and used the saturated saline flotation method and McMaster's method for detection. Molecular examination followed. The overall prevalence was 18.2% (95% confidence interval [CI]: 14.7-22.2%), with Urumqi showing the highest prevalence (29%, 95% CI: 23.4-35.1%) compared to other regions (odds ratio [OR]: 4.62, 95% CI: 2.63-8.41%). Younger camels (≤3 years old) were more likely infected by the parasites after adjusting for the region differences (OR: 10.53, 5.12-24.65%). However, we found no evidence that the prevalence was different between male and female camels. PCR analysis identified Trichostrongylus spp., Chabertia ovina, and Haemonchus contortus as predominant parasites, with observed co-infections indicating a complex parasitic landscape. The findings provide essential epidemiological data for effective parasite control strategies.

Low intestinal parasite prevalence in Finnish pet dogs and cats

BackgroundThis study updates the knowledge of current canine and feline endoparasitic prevalence in Finland. The previous studies reported intestinal worm prevalence of 5.9% in dogs and 7.1% in cats. We also determined the anthelmintic regime and background data of dogs and cats concerning Toxocara spp. infection. Altogether 664 canine and 379 feline (including 46 shelter cats’) fecal samples from over six-month-old animals were examined with quantitative Mini-FLOTAC method using zinc sulfate with a specific gravity of 1.35. Of these samples, 396 canine and 89 feline samples were analyzed using the Baermann method for nematode larvae. A fenbendazole efficacy study was conducted with 12 animals positive for Toxocara spp.ResultsEndoparasites were found in the feces of 3.5% of dogs, 3.6% of pet cats, and 41.3% of shelter cats. The most common findings in dogs were strongylid (1.7%) and Toxocara canis (0.9%) eggs. Trematode (0.4%), Eucoleus spp. (0.3%), taeniid (0.2%), and Trichuris vulpis (0.2%) eggs, and Cystoisospora spp. oocysts (0.2%) were also detected. One dog (0.2%) was positive for Crenosoma vulpis based on the Baermann method. Toxocara cati (3.3%), taeniid (0.6%), and trematode (0.3%) eggs were found in pet cats’ samples. The findings in shelter cat samples were T. cati (34.8%), Eucoleus spp. (13.0%), Cystoisospora spp. oocysts (10.9%), taeniids (8.7%), and Toxoplasma gondii/Hammondia hammondii oocysts (2.2%). Fenbendazole efficacy was adequate in all treated animals, except one cat. The background data revealed 31.2% of dogs being dewormed less than once a year or never. Under twelve-month-old dogs and dogs that were dewormed twice a year were most likely to be T. canis- infected. Shelter cats, male cats, mixed-breed cats, cats that were dewormed two to four times a year, and cats with a history of parasitic infections were most likely to be T. cati infected.ConclusionsThe prevalence of pet canine and feline intestinal parasites in Finland is low, particularly the Toxocara spp. prevalence. In free-roaming cats Eucoleus spp. is surprisingly prevalent. The parasite control strategies reported do not follow the ESCCAP guidelines. Typically, owners deworm their pets only once a year or less frequently.

Anisakis extracellular vesicles elicit immunomodulatory and potentially tumorigenic outcomes on human intestinal organoids

BackgroundAnisakis spp. are zoonotic nematodes causing mild to severe acute and chronic gastrointestinal infections. Chronic anisakiasis can lead to erosive mucosal ulcers, granulomas and inflammation, potential tumorigenic triggers. How Anisakis exerts its pathogenic potential through extracellular vesicles (EVs) and whether third-stage infective larvae may favor a tumorigenic microenvironment remain unclear.MethodsHere, we investigated the parasite's tumorigenic and immunomodulatory capabilities using comparative transcriptomics, qRT-PCR and protein analysis with multiplex ELISA on human intestinal organoids exposed to Anisakis EVs. Moreover, EVs were characterized in terms of shape, size and concentration using classic TEM, SEM and NTA analyses and advanced interferometric NTA.ResultsAnisakis EVs showed classic shape features and a median average diameter of around 100 nm, according to NTA and iNTA. Moreover, a refractive index of 5–20% of non-water content suggested their effective biological cargo. After treatment of human intestinal organoids with Anisakis EVs, an overall parasitic strategy based on mitigation of the immune and inflammatory response was observed. Anisakis EVs impacted gene expression of main cytokines, cell cycle regulation and protein products. Seven key genes related to cell cycle regulation and apoptosis were differentially expressed in organoids exposed to EVs. In particular, the downregulation of EPHB2 and LEFTY1 and upregulation of NUPR1 genes known to be associated with colorectal cancer were observed, suggesting their involvement in tumorigenic microenvironment. A statistically significant reduction in specific mediators of inflammation and cell-cycle regulation from the polarized epithelium as IL-33R, CD40 and CEACAM1 from the apical chambers and IL-1B, GM-CSF, IL-15 and IL-23 from both chambers were observed.ConclusionsThe results here obtained unravel intestinal epithelium response to Anisakis EVs, impacting host’s anthelminthic strategies and revealing for the first time to our knowledge the host-parasite interactions in the niche environment of an emerging accidental zoonosis. Use of an innovative EV characterization approach may also be useful for study of other helminth EVs, since the knowledge in this field is very limited.Graphical

Sex-specific manipulation of sexually cannibalistic mantid mating behavior by hairworms

Abstract Changes in the morphology, physiology, and behavior of parasitized organisms provide an ideal opportunity to examine the extended phenotype of parasites. Because the quality of the host directly affects the fitness of the parasite, parasites may increase their fitness by manipulating phenotypes of low-quality hosts. Males are usually preyed on by females in sexual cannibalism. Thus, the males of sexually cannibalistic species are unsafe and low-quality hosts for parasites, whereas females may be beneficial hosts because of the chance of nutrient intake from cannibalized males. Under passive modes of transmission, parasites cannot choose the host sex. Such parasites exploiting sexually cannibalistic organisms are subjected to contrasting fitness effects and may evolve to manipulate host mating behavior in a sex-specific manner: decreasing male mating to avoid cannibalism and promoting female mating to engage in cannibalism. We examined this hypothesis by a behavioral experiment using a mantid–hairworm system. Parasitized male mantids (Tenodera angustipennis) changed their behavior as expected, exhibiting increased escapes and decreased courtships and mountings, potentially avoiding encounters with the female. Interestingly, male attack behavior was promoted, possibly decreasing contact with the encountered female. However, contrary to our prediction, parasitized females also exhibited decreased propensities of mating, suggesting costs or little benefits of host mating for parasites in the female host. This study provides novel insights into the evolution of parasite strategies in response to sexual differences in host quality.

Deciphering anhydrobiosis and plant parasitism of the wheat seed gall nematode, Anguina tritici through transcriptomic analysis

The wheat seed gall nematode (Anguina tritici L.) poses a significant threat to wheat and barley production. Central to its survival is the ability to endure desiccation through anhydrobiosis, setting it apart from other nematodes. Unraveling the molecular mechanisms governing anhydrobiosis and plant parasitism in A. tritici is crucial for devising effective management strategies. A comprehensive transcriptomic analysis was conducted to elucidate the genetic pathways involved in these processes. Employing next-generation sequencing technologies, gene expression profiling was performed across three developmental stages, namely anhydrobiotic J2, revived J2 and the adult. Transcriptomic profiling yielded 139,002 transcripts in anhydrobiotic J2s, 156,731 in revived J2s, and 80,282 in adult stages, with a cumulative assembly size of 133.2 Mb. Differential gene expression analysis revealed that 1223 genes were significantly upregulated whereas 1934 genes were downregulated in anhydrobiotic J2s in comparison to revived J2s. Comparative transcriptomic analysis across nematode species highlighted conserved and species-specific genes. Functional annotation identified key genes associated with anhydrobiosis, plant parasitism, glycosylation, and longevity mechanisms. Real-time PCR validation corroborated differential expression patterns. The present study provides gene homologs and longevity pathways, which indicate similarity of the mechanism of dauer larva formation and survival strategies to that of Caenorhabditis elegans. Comprehensive understanding of the molecular basis for survival and parasitic strategies of A. tritici, shall provide potential targets for novel control interventions to mitigate nematode's impact on wheat crops.

Dictyocaulosis in cattle: Retrospective analysis of 20 outbreaks in Central Argentina

Bovine lungworms (Dictyocaulus viviparus) are nematodes which cause a respiratory disease known as verminous bronchitis or pneumonia. In this paper, we describe 20 outbreaks of bovine dictyocaulosis recorded between 2000 and 2023 in Central Argentina. Outbreaks occurred more frequently during the autumn-winter season (from April to August) and affected cattle under 1 year old in beef production systems. An average morbidity and mortality of 26.22 % and 8.44 % were registered, respectively. The main clinical signs observed were respiratory distress (coughing, tachypnea, dyspnea, and nasal discharge), weight loss, weakness, decubitus, and diarrhea. Necropsies were performed in thirty-one calves, heifers, and steers. Gross findings included diffuse interstitial or multifocal pneumonia, with marbled appearance intermingling atelectasis and red-gray firm areas of consolidation, and subpleural and interlobular emphysema and edema. Microscopically, lungs were characterized by abundant edema and mixed intra-alveolar multifocal to coalescent infiltrate. Frequently, adult worms and/or larvae were spotted in the bronchi or alveoli, respectively. Some cases exhibited proliferation of type 2 pneumocytes and hyaline membranes covering the alveolar septa. Co-infections with gastrointestinal nematodes were frequently found in fecal samples. Given the perspective of anthelmintic resistance and future changes in environmental conditions due to climate change, integrated parasitic control strategies are mandatory and should be tailored to each production system. The information gathered in this research provides an overview of lungworm infections in livestock production systems from Central Argentina and could be useful for surveilling, monitoring and designing strategic interventions for the control of this important parasitic disease in the region.

Combined high rates of alternative breeding strategies unexpectedly found among populations of a solitary nesting raptor.

Social monogamy is the prevalent mating system in birds, but alternative strategies of extra-pair paternity (EPP) and conspecific brood parasitism (CBP) occur in many species. Raptors are virtually absent in discussions of broad taxonomic reviews regarding EPP and CBP likely because these strategies are mostly absent or at low frequency; CBP is unreported in solitary nesting raptors. In contrast, we found high frequencies of EPP (16%-31%) and CBP (15%-26%) nests among three populations of Cooper's Hawks (Accipiter cooperii) across the northern breeding range of this solitary nesting, socially monogamous species. EPP and CBP combined occurred in 42%-46% of all nests among populations and hence unexpectedly were nearly equivalent to proportions of genetically monogamous nests. Select covariates failed to predict presence of EPP and CBP in part because virtually all extra-pair adults were uncaught and likely were floaters. We found no support for the hypothesis that territorial females traded copulations for food to maximize energy intake for increased production. Our unique discoveries enhance knowledge of the extent and diversity of alternative breeding strategies among groups of avian and other animal species.

Critical and Parasitic Parameters Identification and Frequency Regulation Strategies for UWPT Systems

Critical and Parasitic Parameters Identification and Frequency Regulation Strategies for UWPT Systems

Coordinated molecular and ecological adaptations underlie a highly successful parasitoid.

The success of an organism depends on the molecular and ecological adaptations that promote its beneficial fitness. Parasitoids are valuable biocontrol agents for successfully managing agricultural pests, and they have evolved diversified strategies to adapt to both the physiological condition of hosts and the competition of other parasitoids. Here, we deconstructed the parasitic strategies in a highly successful parasitoid, Trichopria drosophilae, which parasitizes a broad range of Drosophila hosts, including the globally invasive species D. suzukii. We found that T. drosophilae had developed specialized venom proteins that arrest host development to obtain more nutrients via secreting tissue inhibitors of metalloproteinases (TIMPs), as well as a unique type of cell-teratocytes-that digest host tissues for feeding by releasing trypsin proteins. In addition to the molecular adaptations that optimize nutritional uptake, this pupal parasitoid has evolved ecologically adaptive strategies including the conditional tolerance of intraspecific competition to enhance parasitic success in older hosts and the obligate avoidance of interspecific competition with larval parasitoids. Our study not only demystifies how parasitoids weaponize themselves to colonize formidable hosts but also provided empirical evidence of the intricate coordination between the molecular and ecological adaptations that drive evolutionary success.

Unveiling the draft genome of the seed gall nematode, Anguina tritici: Insights and analysis

Anguina tritici, a plant parasitic nematode (PPN) from clade IV of the phylum Nematoda, causes earcockle and tundu diseases in wheat. It stands out from other PPNs due to its ability to parasitize wheat plant seeds and its long-term survival capability under anhydrobiosis conditions within the seeds. Therefore, the genome of A. tritici provides an opportunity to understand the genomic basis for its adaptation to parasitize the aerial parts of the plant. The Illumina MiSeq sequencing strategy yielded a total of 11,065,381,294 bases, with a read count of 40,210,848. The genome, with a size of 164 MB and 39,965 protein-coding genes, was sequenced at 60-fold coverage. Key statistics include a GC content of 39.1 %, Q20 % of 92.73, and Q30 % of 84.08. KEGG analysis identified the involvement of genes in 375 different pathways, highlighting significant pathways related to parasitism, anhydrobiosis, and stress responses. Comparative genomic analysis yielded insightful results regarding the orthologous relationships among the six analyzed species, including A. tritici, Aphelenchoides besseyi, Bursaphelenchus xylophilus, Ditylenchus destructor, Globodera pallida, and Meloidogyne incognita. Sixty-one overlaps were identified, indicating shared orthologous clusters among these species. A single-copy orthologue-based phylogenetic tree showed A. tritici and D. destructor in a monophyletic group. Expert functional annotations revealed the occurrence of several gene homologues involved in developmental processes, neuropeptide signaling, aging, anhydrobiosis, parasitism, RNA interference (RNAi), chemosensory mechanisms, and sex determination processes in A. tritici. These findings offer a comprehensive genetic framework for understanding the parasitism and survival strategies of A. tritici, with significant implications for developing novel control methods and advancing research in plant pathology and Nematology.

Molecular insights and antibody response to Dr20/22 in dogs naturally infected with Dirofilaria repens

Subcutaneous dirofilariasis, caused by the parasitic nematode Dirofilaria repens, is a growing concern in Europe, affecting both dogs and humans. This study focused on D. repens Dr20/22, a protein encoded by an alt (abundant larval transcript) gene family. While well-documented in L3 larvae of other filariae species, this gene family had not been explored in dirofilariasis. The research involved cloning Dr20/22 cDNA, molecular characterization, and evaluating its potential application in the diagnosis of dirofilariasis. Although Real-Time analysis revealed mRNA expression in both adult worms and microfilariae, the native protein remained undetected in lysates from both developmental stages. This suggests the protein’s specificity for L3 larvae and may be related to a process called SLTS (spliced leader trans-splicing), contributing to stage-specific gene expression. The specificity of the antigen for invasive larvae positions it as a promising early marker for dirofilariasis. However, ELISA tests using sera from infected and uninfected dogs indicated limited diagnostic utility. While further research is required, our findings contribute to a deeper understanding of the molecular and immunological aspects of host-parasite interactions and could offer insights into the parasite's strategies for evading the immune system.

The evolution of brood parasitism from host egg predation

Abstract Obligate brood parasites pass all their parental duties to foster parents of a host species. While best understood in birds and hymenopteran insects, obligate brood parasitism has evolved independently at least 59 times across many lineages. The ancestors of brood parasites often provided no parental care to their offspring. Instead, a trophic association with their eventual hosts commonly appears to precede the origin of a brood parasitic strategy. Here, we used a game theoretical model to explore the conditions under which brood parasitism can evolve from predation and be maintained in the population. Our model was inspired by the relationship between the cuckoo catfish (Synodontis multipunctatus) parasitizing mouthbrooding cichlid fishes in the African Lake Tanganyika. Our model demonstrates the facilitatory role of host egg predation on the origin and evolutionary maintenance of brood parasitism through the exploitation of the host response to egg predation by brood parasites. We found no conditions under which brood parasitism as a pure strategy is evolutionarily stable, but we describe a range of evolutionarily stable equilibria when predators and parasites coexist. While our model is tailored to the cuckoo catfish, it generally applies to other systems where brood parasitism has evolved from other antagonistic behavior.

Risk-Based Gastrointestinal Parasite Control in a Tropical Zoological Institute

The surveillance and treatment of parasites are important features of preventative healthcare plans in zoological institutes. The parasite control strategies employed in temperate regions often involve prophylactic anthelmintic treatments during seasons where the burden of gastrointestinal parasites in fecal testing is high. These strategies are, however, not applicable in the tropics, where temperatures remain high throughout the year, allowing continuous parasitic development. A risk-based parasite management strategy was adopted by a tropical zoological institute. For parasite surveillance, routine fecal direct smears and magnesium sulfate flotations were performed to determine parasitic prevalence. The frequency of fecal checks for the year was determined by the frequency at which clinically relevant parasitism (fecal tests that resulted in the animal being treated) was detected during routine fecal checks in the previous year. A yearly anthelmintic drug-class rotation schedule was also implemented. The total number of fecal tests performed per year and the number of animals with clinically significant parasitic disease decreased by 30.0% (637/2126) and 46.9% (207/451), respectively, over the four-year period of the study. Anthelmintic class rotation also improved the efficacy of fenbendazole in treating Strongyloides spp. infecting the group of orangutans. This parasite control strategy is a targeted approach to managing preventative healthcare, reducing the work required to perform routine surveillance tests whilst maintaining the health of the collection of animals.