Blood Meal Research Articles

Minor Hosts Have a Major Impact on the Enzootic Transmission of Borrelia burgdorferi.

In the northeast United States, subadult deer ticks feeding on white-footed mice are thought to drive the force of transmission of Borrelia burgdorferi (B. burgdorferi), the agent of Lyme disease. However, control measures targeting mice have produced inconsistent results, suggesting that other animals are significant contributors to enzootic transmission. Such contributions have previously been difficult to quantify. We used a retrotransposon-based host blood meal assay to measure the relative contribution of hosts to enzootic B. burgdorferi transmission at two insular sites in Massachusetts. Over 6 years, we identified mice and deer as the most common larval hosts at our Nantucket Island site. Infected nymphal ticks were derived mainly from mice (35%) and shrews (31%), despite shrews having fed only 12% of larvae. Deer were identified in 19% of the infected nymphs, despite their known reservoir incompetence. Shrews were consistently the most important host in our Martha's Vineyard site and were identified as the source of 41% of nymphs overall and 39% of the infected nymphs. Sciurids were variable contributors, feeding from 4% to 42% of the larval ticks each year, and contributed no infected nymphs in 2020 and as many as 83% in 2023. We conclude that host contributions to feeding larval ticks change over time and within sites and that shrews may be more influential than mice at some sites. Shrews, sciurids, and even deer may contribute to B. burgdorferi maintenance. Hosts that apparently feed a minor proportion of ticks can have a major impact on the force of B. burgdorferi transmission.

Relationship between malaria vector survival, infectivity, and insecticide-treated net use in western Kenya.

Significant effort and resources have been invested to control malaria transmission in sub-Saharan Africa, but it remains a major public health problem. For the parasite to be transmitted, the female Anopheles vector must survive 10-14days following an infective bite to allow Plasmodium gametocytes to develop into infectious sporozoites. The goal of this study was to assess factors associated with wild-caught Anopheles survival and infection following host-seeking and indoor resting. The study was conducted between January 2020 to March 2022 in a longitudinal cohort of 75 households in 5 villages including a total of 755 household members in Bungoma County, Kenya. Monthly adult mosquito collection was conducted by attenuated aspiration in all enrolled households, and mosquitoes were reared for 7days. The daily mortality rate was determined through day 7. All mosquitoes were morphologically identified. Female Anopheles were dissected, and species-level members of the Anopheles gambiae complex were resolved by molecular methods. The abdomens of all samples were processed for Plasmodium falciparum oocyst detection by PCR. Within a 25-month period, the total numbers of non-Anopheles and Anopheles mosquitoes collected indoors were 12,843 and 712, respectively. Anopheles gambiae and An. funestus were the major vectors, though their distributions varied between different villages; 61.2% (n = 436/712) of the Anopheles mosquitoes survived up to day 7, with the lowest mortality rate recorded on day 5 of captivity. The survival rate also varied between the different Anopheles species. Six hundred eighty-three of 712 mosquito abdomens were tested for P. falciparum; 7.8% (53/683) tested positive for P. falciparum, with An. funestus having a higher (10%) prevalence than An. gambiae s.s. (6.0%, p = 0.095, Pearson Chi-square test). The proportion of household members sleeping under a bednet the night before mosquito collection varied across time and village. Anopheles funestus survival times were refractory to household ITN usage, and An. gambaie s.s. survival was reduced only under very high (100%) ITN usage. Despite ITN usage, mosquitoes still acquired blood meals and P. falciparum infections. Survival differed across species and was inversely correlated with high ITN usage in the household but not oocyst development.

The Plasmodium transmission-blocking symbiont, Microsporidia MB, is vertically transmitted through Anopheles arabiensis germline stem cells.

Microsporidia MB is a promising candidate for developing a symbiont-based strategy for malaria control because it disrupts the capacity of An. arabiensis to transmit the Plasmodium parasite. The symbiont is predominantly localized in the reproductive organs and is transmitted vertically from mother to offspring and horizontally (sexually) during mating. Due to the contribution of both transmission routes, Microsporidia MB has the potential to spread through target vector populations and become established at high prevalence. Stable and efficient vertical transmission of Microsporidia MB is important for its sustainable use for malaria control, however, the vertical transmission efficiency of Microsporidia MB can vary. In this study, we investigate the mechanistic basis of Microsporidia MB vertical transmission in An. arabiensis. We show that vertical transmission occurs through the acquisition of Microsporidia MB by Anopheles cystocyte progenitors following the division of germline stem cells. We also show that Microsporidia MB replicates to increase infection intensity in the oocyte of developing eggs when mosquitoes take a blood meal suggesting that symbiont proliferation in the ovary is coordinated with egg development. The rate of Microsporidia MB transmission to developing eggs is on average higher than the recorded (mother to adult offspring) vertical transmission rate. This likely indicates that a significant proportion of An. arabiensis offspring lose their Microsporidia MB symbionts during development. The stability of germline stem cell infections, coordination of symbiont proliferation, and very high rate of transmission from germline stem cells to developing eggs indicate that Microsporidia MB has a highly specialized vertical transmission strategy in An. arabiensis, which may explain host specificity.

Effects of fasting on the interplay between temperature and Trypanosoma cruzi infection on the life cycle of the Chagas disease vector Rhodnius prolixus.

Rhodnius prolixus, a triatomine insect, is one of the most important vectors of Chagas disease in South America. Its interaction with the parasite Trypanosoma cruzi, the causative agent of this disease, is known to be deeply affected by ambient temperature and the nutritional status of the insect vector. In this study, we investigated how starvation affects the life cycle of R. prolixus and the population dynamics of the parasite inside the intestine of the vector at four temperatures ranging from 24°C to 30°C. The weights and molting times of chronically infected and uninfected insects were monitored through repeated 30-day fasting periods from first instar to adult stage, assessing their capacity to retain blood meal weight between developmental stages and tracking parasite concentrations in their urine. Our results demonstrate that ambient temperature is a crucial factor affecting the resistance of R. prolixus to starvation, as survival, body weight, and weight retention greatly decreased in high temperature treatments. Furthermore, we showed that temperature significantly influenced whether T. cruzi established an infection in early instars, with few insects developing infections at the lowest and highest temperature treatments. Additionally, we discovered that a fasting period of 30 days induces a steady decrease in parasite populations in the vector over its lifetime. Infection by T. cruzi had no effect on the survival, molting time, and nutritional factors monitored in our protocol. Our results highlight the importance of nutrition as a determining factor for the development of the vector and the parasite, providing valuable insights for elucidating the complex interplay between temperature and nutrition in shaping the epidemiology of Chagas disease in a changing climate.

New record of Carnidae (Diptera) from Taiwan and potential challenges in DNA barcode amplification due to pseudogene

The genus Carnus Nitzsch, 1818 comprises small ectoparasites that feed on the blood of juvenile avians. They are characterised by dealated adults with setose abdominal intersegmental membranes. Carnus orientalis Maa, 1968 was previously recorded in Malaysia and the Ryukyu Islands of Japan, parasitising two owl species: Ketupa ketupu (Horsfield, 1821) and Otus elegans (Cassin, 1852). This study confirms the occurrence of C. orientalis in Taiwan and presents a new host record, along with COI barcode sequences. Additionally, the study also elucidates the difficulties posed by blood meal contamination and pseudogene amplification as confounding factors intrinsic to the molecular taxonomic delineation of C. orientalis via universal DNA barcoding primers. The following new information regarding C. orientalis is provided in this study: Carnus orientalis is first recorded in Taiwan, filling the gap in its East Asian distribution. This is also the first record of Carnidae from Taiwan. Otus lettia (Hodgson, 1836) (Aves, Strigidae) is reported as a new host for C. orientalis, identified on a fallen fledgling. Co-amplification of the host's COI is reported in this study using the universal PCR primer set LCO1490/HCO2198. Additionally, the amplification of a COI-like pseudogene using a newly-designed primer set is detected through abnormal translated amino acid sequences and the occurrence of a stop codon. New specific primers for the COI gene of Carnus were designed in this study. Carnus orientalis is first recorded in Taiwan, filling the gap in its East Asian distribution. This is also the first record of Carnidae from Taiwan. Otus lettia (Hodgson, 1836) (Aves, Strigidae) is reported as a new host for C. orientalis, identified on a fallen fledgling. Co-amplification of the host's COI is reported in this study using the universal PCR primer set LCO1490/HCO2198. Additionally, the amplification of a COI-like pseudogene using a newly-designed primer set is detected through abnormal translated amino acid sequences and the occurrence of a stop codon. New specific primers for the COI gene of Carnus were designed in this study. The new distribution and ecological data of C. orientalis enhance our understanding of this species. The provision of new COI primers is anticipated to contribute to future studies employing DNA barcoding in bird-parasitic flies. The following new information regarding C. orientalis is provided in this study: Carnus orientalis is first recorded in Taiwan, filling the gap in its East Asian distribution. This is also the first record of Carnidae from Taiwan. Otus lettia (Hodgson, 1836) (Aves, Strigidae) is reported as a new host for C. orientalis, identified on a fallen fledgling. Co-amplification of the host's COI is reported in this study using the universal PCR primer set LCO1490/HCO2198. Additionally, the amplification of a COI-like pseudogene using a newly-designed primer set is detected through abnormal translated amino acid sequences and the occurrence of a stop codon. New specific primers for the COI gene of Carnus were designed in this study. Carnus orientalis is first recorded in Taiwan, filling the gap in its East Asian distribution. This is also the first record of Carnidae from Taiwan. Otus lettia (Hodgson, 1836) (Aves, Strigidae) is reported as a new host for C. orientalis, identified on a fallen fledgling. Co-amplification of the host's COI is reported in this study using the universal PCR primer set LCO1490/HCO2198. Additionally, the amplification of a COI-like pseudogene using a newly-designed primer set is detected through abnormal translated amino acid sequences and the occurrence of a stop codon. New specific primers for the COI gene of Carnus were designed in this study. The new distribution and ecological data of C. orientalis enhance our understanding of this species. The provision of new COI primers is anticipated to contribute to future studies employing DNA barcoding in bird-parasitic flies.

Role of Tick Commensal Bacteria in the Propagation of Emerging Infectious Diseases: Data Gaps and One Health Implications

Ticks are obligate hematophagous ectoparasites notorious for their role as vectors of pathogens that affect humans and animals, particularly relative to the propagation of emerging infectious diseases (EIDs). Two important factors facilitating the role of ticks in the propagation of EIDs are their potential for the development of resistance to acaricides and the expansion of nonindigenous tick species into new geographic regions. The acquisition of acaricide resistance enables tick populations to be less susceptible to vector control programs. Expansion of the geographic distribution of tick populations increases the likelihood of access to new host species as well as new pathogens. Understanding of the microbiome of ticks continues to evolve, providing critical insights into tick biology. The tick microbiome largely comprises endosymbionts, pathogenic organisms, and commensal bacteria. Endosymbionts are highly preserved and vertically transmitted in ticks from mother to offspring, and their role in the survival of ticks is well recognized. Similarly, the role of ticks as vectors of pathogens is well established. However, commensal bacteria in ticks are acquired from the environment and while ingesting a blood meal. Because many tick species spend most of their lifetime off the hosts, it can be assumed that the richness and diversity of commensal bacteria are highly variable and dependent on the ecosystem in which the tick exists. This mini-review identifies some of the critical data gaps relevant to the role of and influence of commensal bacteria on the vectorial capacity of ticks. As ticks move into new habitats, are locally acquired commensal bacteria playing a role in adaptation to the new habitat? Apart from the conventionally understood mechanisms of acaricide resistance in ticks, are the commensal bacteria influencing the development of acaricide resistance at the population level?

Child health, nutrition and gut microbiota development during the first two years of life; study protocol of a prospective cohort study from the Khyber Pakhtunkhwa, Pakistan

Recent evidence suggests that the development of gut microbiota during infancy affects several metabolic, immune, and endocrine pathways in humans. An imbalance in gut microbiota diversity or function, also known as dysbiosis, not only affects early child growth and development, but is also linked with the development of chronic, non-communicable diseases in later life. The Child Health And Microbiome Development Study – Pakistan (CHAMP) study aimed to longitudinally assess gut microbiota development and associated factors (maternal, child, and demographic) during early childhood in populations residing in malnutrition-endemic communities in Pakistan. A prospective cohort of mother-infant pairs (n=70) will be recruited from District Swat, Pakistan, and followed for two years. Complete information about demographic characteristics, anti-natal and post-natal care, dietary intake, feeding practices, and child health will be collected at baseline and 3, 6, 12, 18, and 24 months. Anthropometric measurements (height, weight, mid-upper arm circumference, and head circumference), dry blood spots, and fecal samples were also collected. Ethical approval for the study was obtained from Khyber Medical University, Pakistan. The study is also registered on clincaltrial.gov (Ref no: NCT05793294). The study findings will help researchers understand gut microbiota development, associated factors, and their impact on longitudinal growth in infants during the first two years of life.

Phlebotomine sand fly survey, blood meal source identification, and description of Sergentomyia imihra n. sp. in the central Sahara of Algeria

BackgroundPhlebotomine sand flies (Diptera: Psychodidae) are important vectors of various pathogens, mainly Leishmania parasites. In the Old World, the most important genus in term of pathogens transmission is the genus Phlebotomus, which includes many proven or suspected vectors of several Leishmania species, while the genus Sergentomyia remains so far unproven as a vector of human pathogens. Algeria is one of the most affected countries by human leishmaniasis.MethodsIn the present study, an entomological survey was carried out in two provinces, Ghardaïa and Illizi, located in the north and central Sahara, respectively, where cases of human leishmaniasis are recorded. Our goal was to understand the role of the local sand fly species in the transmission of Leishmania parasites and to analyze their blood meal preferences. Collected sand flies were identified by a combination of morphological and molecular approaches that included DNA-barcoding and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) protein profiling. In addition, female blood meals were analyzed by peptide mass mapping using MALDI-TOF MS.ResultsIn total, 640 sand fly specimens belonging to Phlebotomus and Sergentomyia genera were collected in the two provinces. Sergentomyia antennata and Se. fallax were most abundant species in Ghardaïa, and Ph. papatasi and Ph. alexandri in Illizi. In addition, a new sand fly species was described in Illizi named Sergentomyia (Sergentomyia) imihra n. sp. Blood meal analysis of the engorged females revealed various mammalian hosts, especially goats, but also humans for Phlebotomus papatasi and Ph. alexandri, suggesting that these vector species are opportunistic feeders.ConclusionsIntegrative approach that combined morphological analysis, sequencing of DNA markers, and protein profiling enabled the recognition and description of a new Sergentomyia species, raising the number of the Algerian sand fly fauna to 27 species. Further sand fly surveillance in the central Sahara is recommended to identify the thus-far unknown males of Se. imihra n. sp.Graphical

Differential sensitivity and specificity of Aedes aegypti and Anopheles gambiae to adenine nucleotide phagostimulants—an all-or-none response?

BackgroundThe decision to imbibe a blood meal is predominantly dependent on the sensitivity and specificity of haematophagous arthropods to blood-derived adenine nucleotides, in particular adenosine triphosphate (ATP). Despite previous efforts to identify and characterise the specificity and sensitivity to ATP and other adenine nucleotides, as well as the role of other blood-derived phagostimulants across the Culicidae, comparisons across species remain difficult.MethodsThe feeding response of the yellow fever mosquito Aedes aegypti and the African malaria vector Anopheles gambiae to adenine nucleotides in the presence of a carbonate buffer was assessed using a membrane feeding assay. The proportion of mosquitoes engorged and the volume imbibed by all mosquitoes was scored visually and spectrophotometrically. In addition, the proportion of prediuresing An. gambiae, as well as the volume engorged and prediuresed, was examined.ResultsAedes aegypti was more sensitive to adenine nucleotides than An. gambiae, but both species maintained specificity to these phagostimulants, demonstrating a dose-dependent bimodal feeding pattern, thereby expanding our understanding of the all-or-none blood-feeding hypothesis. Feeding on the bicarbonate buffer by An. gambiae—but not that of Ae. aegypti—demonstrated a species-specific variation in how blood phagostimulants are encoded. Adenine nucleotides, with and without bovine serum albumin, were observed to dose-dependently regulate the proportion of An. gambiae prediuresing and the volumes prediuresed but not volumes engorged.ConclusionsTaken together, the results of this study expand our understanding of how mosquitoes differentially assess and respond to blood meal constituents, and provide a basis for further physiological and molecular studies.Graphical

Phosphoproteomics Analyses of Aedes aegypti fat body reveals blood meal-induced Signaling and Metabolic Pathways.

The mosquito fat body is the principal source of yolk protein precursors (YPP) during mosquito egg development in female Aedes aegypti. To better understand the metabolic and signaling pathways involved in mosquito reproduction, we investigated changes in the mosquito fat body phosphoproteome at multiple time points after a blood meal. Using LC/MS, we identified 3,570 phosphorylated proteins containing 14,551 individual phosphorylation sites. We observed protein phosphorylation changes in cellular pathways required for vitellogenesis, as well as proteins involved in primary cellular functions. Specifically, after a blood meal, proteins involved in ribosome synthesis, transcription, translation, and autophagy showed dynamic changes in their phosphorylation patterns. Our results provide new insight into blood meal-induced fat body dynamics and reveal potential proteins that can be targeted for interference with mosquito reproduction. Considering the devastating impact of mosquitoes on human health, worldwide, new approaches to control mosquitoes are urgently needed.

Vampire bats rapidly fuel running with essential or non-essential amino acids from a blood meal.

In most mammals, running is fuelled by oxidization of endogenous carbohydrates and lipids while amino acids contribute little (< 5-10%). Common vampire bats (Desmodus rotundus), however, specialize on a unique, protein-rich blood diet. Therefore, we hypothesized that (i) vampire bats would rapidly begin utilizing dietary amino acids to support running metabolism, and (ii) that relative reliance on essential and non-essential amino acids would be similar. We fed bats cow's blood enriched either with isotopically labelled glycine (non-essential amino acid) or leucine (essential amino acid). Bats were exercised at speeds of 10, 20 and 30 m min-1 on a respirometry treadmill, allowing us to assess metabolic rate (i.e. O2 consumption and CO2 production) and track the oxidation of labelled amino acids in exhaled CO2. Vampire bats oxidized amino acids as their primary fuel as indicated by a respiratory exchange ratio (RER = ratio of CO2 production to O2 consumption rates) of approximately 0.8-0.9 at all speeds, with the labelled meal accounting for as much as 60% of oxidized fuels at peak usage. Similar oxidation rates indicated bats did not discriminate between essential and non-essential amino acid use. These findings reiterate how strongly metabolism can be shaped by a specialized diet.

Seasonal haemosporidian detection in mosquitoes (Diptera: Culicidae) and their interactions with vertebrate hosts in a Mexican cloud forest.

Studies on avian haemosporidians in Mexico and around the world reveal poor knowledge about the vectors that transmit avian haemosporidian parasites and their association with vertebrate hosts. Seasonal variations given by changes in temperature and precipitation have significant repercussions on the dynamics of vector-borne infections. The seasonal dynamics of major haemosporidian parasites and their main vectors are mostly unknown. This study aimed to determine the presence of avian haemosporidians in hematophagous mosquitoes and to characterize mosquito-vertebrate host interactions during a year in a peri-urban cloud forest in Xalapa City, Veracruz, Mexico. We analyzed 12 species and a total of 1170 hematophagous mosquitoes. We found the presence of Plasmodium and Haemoproteus genera in the blood meals of mosquitoes. The highest haemosporidian detection and mosquito richness were in June (dry-warm season), whereas the highest mosquito abundance was in October (humid-warm season). We recorded three new haemosporidian lineages in this study. Analysis of blood meals showed that mosquitoes fed on different vertebrate groups (amphibians, reptiles, birds, and humans). This study contributed to the knowledge about the distribution of hematophagous mosquito-haemosporidian-vertebrate host interactions.

Climate‐associated variation in the within‐season dynamics of juvenile ticks in California

AbstractChanging climate has driven shifts in species phenology, influencing a range of ecological interactions from plant–pollinator to consumer–resource. Phenological changes in host–parasite systems have implications for pathogen transmission dynamics. The seasonal timing, or phenology, of peak larval and nymphal tick abundance is an important driver of tick‐borne pathogen prevalence through its effect on cohort‐to‐cohort transmission. Tick phenology is tightly linked to climatic factors such as temperature and humidity. Thus, variation in climate within and across regions could lead to differences in phenological patterns. These differences may explain regional variation in tick‐borne pathogen prevalence of the Lyme disease‐causing Borrelia bacteria in vector populations in the United States. For example, one factor thought to contribute to high Lyme disease prevalence in ticks in the eastern United States is the asynchronous phenology of ticks there, where potentially infected nymphal ticks emerge earlier in the season than uninfected larval ticks. This allows the infected nymphal ticks to transmit the pathogen to hosts that are subsequently fed upon by the next generation of larval ticks. In contrast, in the western United States where Lyme disease prevalence is generally much lower, tick phenology is thought to be more synchronous with uninfected larvae emerging slightly before, or at the same time as, potentially infected nymphs, reducing horizontal transmission potential. Sampling larval and nymphal ticks, and their host‐feeding phenology, both across large spatial gradients and through time, is challenging, which hampers attempts to conduct detailed studies of phenology to link it with pathogen prevalence. In this study, we demonstrate through intensive within‐season sampling that the relative abundance and seasonality of larval and nymphal ticks are highly variable along a latitudinal gradient and likely reflect the variable climate in the far western United States with potential consequences for pathogen transmission. We find that feeding patterns were variable and synchronous feeding of juvenile ticks on key blood meal hosts was associated with mean temperature. By characterizing within‐season phenological patterns of the Lyme disease vector throughout a climatically heterogeneous region, we can begin to identify areas with high potential for tick‐borne disease risk and underlying mechanisms at a finer scale.

Temperature and photoperiod differentially impact maternal phenotypes in diapause egg-laying Aedes albopictus mosquitoes.

Aedes albopictus (Skuse 1894) mosquitoes can transmit deadly arboviruses and are globally invasive due to their ability to survive in both tropical and temperate climates. Although adults cannot survive harsh winters, females are capable of anticipating seasonal change and producing overwintering diapause (DP) eggs that remain in a state of arrested development over the winter and hatch when favorable conditions return in the spring. While low temperatures can facilitate DP entry under short photoperiods, temperature signals alone are not sufficient to induce DP. To identify maternal phenotypes predictive of DP egg production in laboratory conditions, we characterized aspects of maternal physiology and behavior to identify those that correlate with DP egg production and changes in photoperiod, versus changes in temperature. Neither changes in temperature nor photoperiod impacted protein preference, blood meal consumption, or total number of eggs produced per female. Egg retention and oviposition timing were influenced by temperature, independent of DP egg production. However, females housed under short photoperiod conditions showed increased starvation resistance, despite showing similar levels of locomotor activity and internal stores of triacylglycerols, glucose, glycogen, and trehalose compared to females housed in long photoperiods. These results suggest that temperature and photoperiod differentially affect maternal phenotypes and identify starvation resistance as a maternal phenotype that is influenced by photoperiod and correlates with DP egg status.

The glycoprotein hormone receptor (LGR1) influences Malpighian tubule secretion rate in Rhodnius prolixus.

In the hemipteran Rhodnius prolixus, successful post-prandial diuresis is accomplished through the synergistic actions of the peptidergic diuretic hormone RhoprCRF/DH and the biogenic amine 5-hydroxytryptamine (5-HT), and by an antidiuretic hormone RhoprCAPA-2 that terminates diuresis by inhibiting this synergy. Lateral neurosecretory cells (NSCs) in the mesothoracic ganglionic mass release RhoprCRF/DH, while midline NSCs release RhoprCAPA-2 during blood feeding. These NSCs co-express GPA2/GPB5, a conserved glycoprotein hormone involved in various physiological processes across bilaterians. This study investigates the influence of GPA2/GPB5 signaling on Malpighian tubule (MT) fluid secretion in R. prolixus. GPB5-like immunoreactivity in lateral and midline NSCs decreases following a blood meal, suggesting release and a role in diuresis. Downregulating the GPA2/GPB5 receptor LGR1 via RNA interference results in an increased basal fluid secretion rate in MTs, which is inhibited by the antidiuretic hormone RhoprCAPA-2. dsLGR1 treatment reduces the effects of RhoprCRF/DH and 5-HT on MT secretion and eliminates their synergism. RT-qPCR reveals that the transcript expression of the diuretic and antidiuretic hormone receptors are decreased in MTs of dsLGR1 injected insects, indicating that GPA2/GPB5 influences the expression of these other receptor transcripts. Downregulating LGR1 results in a smaller blood meal size and disrupts the normal time-course of diuresis. As LGR1 is the most abundantly expressed G protein-coupled receptor transcript in R. prolixus MTs, our results suggest that GPA2/GPB5 signaling has a critical role in regulating the timing and success of water retention in the unfed state, and in the complex processes associated with feeding and diuresis in R. prolixus.

Late gestation maternal infection with bovine viral diarrhea virus impacts offspring feedlot performance, digestion, blood parameters, and hot carcass weights.

Fetal infection with bovine viral diarrhea virus (BVDV) after 150 d results in transient fetal infections (TI). Twenty-five unvaccinated, yearling Hereford heifers, seronegative for antibodies to BVDV1 and BVDV2, were bred by artificial insemination with X chromosome-bearing sperm from one Angus sire to examine the impact of TI on postnatal growth, estimated dry matter digestibility, blood parameters, and carcass characteristics. On d 175 of pregnancy, dams were intranasally inoculated with either sham control or 4.0 log median tissue culture infectious dose noncytopathic type2 BVDV to generate control or TI offspring, respectively. All control dams remained seronegative and all BVDV-inoculated dams seroconverted by d 14 post-inoculation. All control offspring were seronegative and all TI offspring were seropositive for antibodies to type 2 BVDV at birth. All offspring were raised on pasture until weaning. At weaning, all calves were transported to our research feedlot facility, housed in three pens, and transitioned to a high-energy concentrate-based diet. Heifer body weights (BW) and jugular blood samples were collected every 28 d. On d 84 of the feeding period, titanium dioxide was added to the diet of 12, age-paired, individually fed, heifers (6 control and 6 TI heifers; approximately 1 yr. of age) for 28 d and used to estimate dry matter digestibility. On d 105 and 240 ruminal fluid (approximately 900ml) was collected from every animal using a stomach pump and analyzed for short chain fatty acids (SCFA). After approximately 287 d on feed, heifers were transported to a USDA-inspected abattoir and harvested. TI heifers had lighter final BW (P < 0.04) when compared to control heifers. Average daily gain was greater (P < 0.01) in control compared to TI heifers. TI heifers had a 2.2% lesser (P < 0.05) apparent dry matter digestibility, lighter (P < 0.01) hot carcass weights, but similar ruminal SCFA compared to controls. Blood glucose concentrations were similar (P > 0.8) between control and TI heifers. Ceruloplasmin activity (P < 0.03) and the oxidized form of glutathione (GSSG; P < 0.01), indicators of chronic inflammation, were increased in plasma from TI heifers compared to controls. Other indicators of oxidative stress were not impacted (P > 0.10) by TI status. These data suggest that fetal BVDV transient infection negatively impacts growth throughout the feeding period, possibly by impacting gastrointestinal tract function and increasing systemic inflammation.

Use of blood meals from stable flies to evaluate the bovine leukemia virus infection status in cattle herds: a pilot study.

The incidence of enzootic bovine leukosis (EBL), a type of B-cell lymphoma, is increasing in Japan. EBL is caused by bovine leukemia virus (BLV; Retroviridae, Deltaretrovirus bovleu) infection and is diagnosed by detecting antibodies against BLV in milk and blood or BLV DNA in blood. We assessed the feasibility of using stable flies (Stomoxys calcitrans) as a sampling tool to assess BLV infection status in cattle herds. First, we collected blood from 3 cattle herds and, based on the measurement of BLV-proviral load (PVL) by quantitative real-time PCR (qPCR), identified 1) a BLV-free herd, 2) a herd with a low prevalence of BLV-infected cattle and low PVL, and 3) a herd wherein half of the cattle were BLV-infected with low-to-high PVLs. Next, we collected stable flies from the 3 herds, extracted DNA from their blood meals, analyzed it for BLV DNA, and measured the BLV PVL. Cattle DNA and BLV DNA, but not other mammalian DNA, were successfully detected by digestion of the flies. Based on fly blood meal qPCR, we identified one herd as BLV-free and the other 2 herds as having <50% prevalence of BLV-infected cattle with low PVLs. Our fly results were not consistent with preliminary BLV-PVL measurements on cattle blood. Our pilot study indicated that, to assess the feasibility of a stable fly blood meal test as an alternative technique for evaluating BLV infection status in dairy and beef cattle, additional investigations involving more cattle herds and stable flies are needed.

Bat-associated ticks as a potential link for vector-borne pathogen transmission between bats and other animals.

Potentially zoonotic pathogens have been previously detected in bat-associated ticks, but their role in disease transmission and their frequency of feeding on non-bat hosts is poorly known. We used molecular blood meal analysis to reveal feeding patterns of the bat-associated tick species Ixodes ariadnae, I. simplex, and I. vespertilionis collected from cave and mine walls in Central and Southeastern Europe. Vertebrate DNA, predominantly from bats, was detected in 43.5% of the samples (70 of 161 ticks) but in these ticks we also detected the DNA of non-chiropteran hosts, such as dog, Canis lupus familiaris, wild boar, Sus scrofa, and horse, Equus caballus, suggesting that bat-associated ticks may exhibit a much broader host range than previously thought, including domestic and wild mammals. Furthermore, we detected the zoonotic bacteria Neoehrlichia mikurensis in bat ticks for the first time, and other bacteria, such as Bartonella and Wolbachia. In the light of these findings, the role of bat ticks as disease vectors should be urgently re-evaluated in more diverse host systems, as they may contribute to pathogen transmission between bats and non-chiropteran hosts.

Assessing the impact of a potential canine vaccine for the control of Chagas disease: a mathematical modeling study

IntroductionChagas disease, a zoonotic infection transmitted by triatomine bugs, poses serious public health risks in endemic areas. As dogs are important reservoirs in the disease’s spread, developing a canine vaccine could be transformative for controlling disease transmission to dogs and humans.MethodsWe developed a compartmental Susceptible-Infected model to simulate the transmission dynamics of Trypanosoma cruzi, considering interactions among dogs, humans, cats, rodents, and triatomine vectors. We used the model to assess the direct and indirect impacts of two vaccine mechanisms—all-or-nothing and leaky—on disease incidence across different host populations. The sensitivity of the model’s outcomes to changes in input parameters was analyzed using univariate sensitivity analysis.ResultsOur model showed that with a 90% vaccine efficacy, an all-or-nothing vaccine could reduce the cumulative incidence of T. cruzi in dogs by 91.3% over five years. The 60% and 30% vaccine efficacies would result in reductions of 63.47% and 33%, respectively, over 5 years. Similarly, the leaky vaccine achieved a 92.62% reduction in dog infections over 5 years with 90% efficacy. The indirect effects on human T. cruzi infection were notable; the all-or-nothing vaccine reduced human disease incidence by 14.37% at 90% efficacy, while the leaky vaccine achieved a 32.15% reduction over 5 years. Both vaccine mechanisms may substantially reduce T. cruzi incidence among dogs, and generate indirect benefit to other hosts, such as humans, by reducing their infection risk. The indirect benefits of vaccination were heavily influenced by the proportion of triatomine bugs blood meals taken from dogs.DiscussionThe study highlights the potential of targeted canine vaccination in controlling Chagas disease transmission and burden in endemic countries. It provides additional evidence for pursuing the development of a canine vaccine as a valuable tool for Chagas disease elimination.

Exploring the longitudinal expression dynamics of midguts in adult female Amblyomma americanum ticks

BackgroundFemale ticks remain attached to their host for multiple days to complete a blood meal. This prolonged feeding period is accompanied by a significant increase in the tick’s size and body weight, paralleled by noteworthy changes to the tick midgut. While the midgut is recognized for its established role in blood storage and processing, its importance extends to playing a crucial role in the acquisition, survival, and proliferation of pathogens. Despite this, our overall understanding of tick midgut biology is limited.ResultsOur transcriptome analysis identified 15,599 putative DNA coding sequences (CDS), which were classified into 26 functional groups. Dimensional and differential expression analyses revealed four primary transcriptional profiles corresponding to unfed, slow-feeding, transitory (from slow- to rapid-feeding), and rapid-feeding stages. Additionally, comparing the current dataset with previously deposited transcriptome from other tick species allowed the identification of commonly expressed transcripts across different feeding stages.ConclusionOur findings provide a detailed temporal resolution of numerous metabolic pathways in the midgut of A. americanum adult females throughout the feeding process, highlighting the dynamic transcriptional regulation of the tick’s midgut as feeding progresses. Furthermore, we identified conserved transcripts across three different tick species that exhibit similar expression patterns. This knowledge not only enhances our understanding of the physiological processes within the tick midgut but also opens up potential avenues for developing control methods that target multiple tick species.