Non-imported malaria in non-endemic countries: a review of cases in Spain

Modelling the spatial risk of malaria through probability distribution of Anopheles maculipennis s.l. and imported cases

Malaria remains one of the most important infectious diseases globally due to its high incidence and mortality rates. The influx of infected cases from endemic to non-endemic malaria regions like Europe has resulted in a public health concern over sporadic local outbreaks. This is facilitated by the continued presence of competent Anopheles vectors in non-endemic countries.We modelled the potential distribution of the main malaria vector across Spain using the ensemble of eight modelling techniques based on environmental parameters and the Anopheles maculipennis s.l. presence/absence data collected from 2000 to 2020. We then combined this map with the number of imported malaria cases in each municipality to detect the geographic hot spots with a higher risk of local malaria transmission.The malaria vector occurred preferentially in irrigated lands characterized by warm climate conditions and moderate annual precipitation. Some areas surrounding irrigated lands in northern Spain (e.g. Zaragoza, Logroño), mainland areas (e.g. Madrid, Toledo) and in the South (e.g. Huelva), presented a significant likelihood of A. maculipennis s.l. occurrence, with a large overlap with the presence of imported cases of malaria.While the risk of malaria re-emergence in Spain is low, it is not evenly distributed throughout the country. The four recorded local cases of mosquito-borne transmission occurred in areas with a high overlap of imported cases and mosquito presence. Integrating mosquito distribution with human incidence cases provides an effective tool for the quantification of large-scale geographic variation in transmission risk and pinpointing priority areas for targeted surveillance and prevention.

Screening blood donors for malaria, can we increase the number of eligible donors? An observational retrospective study

BACKGROUND

In non-endemic countries, malaria can be transmitted through blood donations from imported cases. To ensure standards of quality and safety of human blood, the European Union and Spanish national law, requires a deferral period, or a screening by immunological or genomic test among those donors with potential risk of malaria. Scientific societies, European Committee on Blood Transfusion, and Spanish Society of Haematology and Haemotherapy, refer only to the result of the immunological test.

METHODS

An observational retrospective study was performed in potential donors with a positive immunological test for malaria done in the Regional Transfusion Center in Madrid and referred to the National Reference Unit for Tropical Diseases in Madrid between 2015-2020. At consultation a Polymerase Chain Reaction (PCR) for malaria was performed.

RESULTS

During the study period, 121 possible donors attended for consultation at NRU-Trop. Median age: 38.5 (IQR:33-48); median time to consultation was 32 months (IQR:12.5-110). Eighty-two (67.8%) donors were migrants and thirty-nine were travellers (32.2%). ELISA values were available for 109 subjects (90.1%), 56 individual left malaria endemic area > 3 years before. All donors tested negative for Plasmodium spp PCR test (n = 121, 100%).

CONCLUSIONS

None of the subjects with a positive immunologic test deferred as blood donors had a positive genomic test. The presence of Plasmodium spp in collected blood was not detected by molecular techniques. To avoid the loss of potential blood donors, especially those with low incidence red blood cell antigens, as more precise microbiology techniques become available, updating the existing legislation becomes necessary to increase the availability of donated blood.

Investigation of an airport-associated cluster of falciparum malaria in Frankfurt, Germany, 2022

Airport malaria is uncommon but increasing in Europe and often difficult to diagnose. We describe the clinical, epidemiological and environmental investigations of a cluster of airport malaria cases and measures taken in response. Three Frankfurt International Airport employees without travel histories to malaria-endemic areas were diagnosed with Plasmodium falciparum malaria in Germany in 2022. Two cases were diagnosed within 1 week, and the third one after 10 weeks. Two cases had severe disease, all three recovered fully. The cases worked in separate areas and no specific location for the transmissions could be identified. No additional cases were detected among airport employees. In June and July, direct flights from Equatorial Guinea, Nigeria and Angola and one parcel originating in Ghana arrived at Frankfurt airport. No vector-competent mosquitoes could be trapped to identify the source of the outbreak. Whole genome sequencing of P. falciparum genomes showed a high genetic relatedness between samples of the three cases and suggested the geographical origin closest to Ghana. A diagnosis of airport malaria should prompt appropriate and comprehensive outbreak investigations to identify the source and to prevent severe forms of falciparum malaria.

Intracellular Pathogens: Infection, Immunity, and Intervention

Intracellular pathogens comprise a diverse group of pathogens that all share a required location in a host cell to infect, survive, and replicate. Intracellular location allows pathogens to hide from host immune responses, avoid competition with other pathogens, mediate host cellular functions, replicate safely, and cause infection that is difficult to target with therapeutics. All intracellular pathogens have varying routes of infiltration into host cells and different host cell preferences. For example, bacteria Mycobacterium tuberculosis chooses to invade antigen-presenting cells, which allows them to moderate host antigen presentation to memory cells, whereas rabies virus prefers to invade neurons because they have pre-existing innate immunity protection systems. Regardless of the pathway that each intracellular pathogen follows, all share the capacity to cause disease if they succeed in entering host cells. Here, we give an overview of selected intracellular pathogens and infections they cause, immune responses they induce, and intervention strategies used to treat and control them.

Factors Contributing to the Pre-Elimination of Malaria from Hainan Island, China, 1986-2009

Malaria was endemic in Hainan Island, China, for a lengthy period before its elimination. Here, we aim to gain a better understanding of malaria elimination by assessing and quantifying the relative effects of longitudinal changes in specific antimalarial interventions, socioeconomic development approaches, and malaria vectors on malaria prevalence in Hainan during the 1986-2009 pre-elimination period. Annual data were collected on the incidence of malaria, the number of residents protected by drugs (RPD), the number of residents protected by vector control, the presence of Anopheles minimus and Anopheles dirus, the annual per capita income of rural residents, major cash crop (rubber plantation) areas, the literacy rate of adult rural residents, and the rate of reinforced concrete house construction in rural areas. Backward stepwise multiple linear regression models were developed to identify the factors associated with the annual malaria incidence (AMI). The AMI declined from 20.3 to 0.8 per 10,000 population from 1986 to 2009; this decrease was significantly associated with an increase in the number of RPD and improved literacy rate among rural adults. The results of this study implied that the sustained distribution of antimalarial drugs and increase in education levels in risk areas significantly impacted the reduction and elimination of malaria infection in Hainan. We suggest that these findings could be applicable to malaria-endemic areas in Southeast Asia with similar natural and socioeconomic environments to Hainan and where malaria incidence has decreased to a low level.

Tracking the geographical origin of Plasmodium falciparum causing a rare severe case of malaria imported into Palestine, a zero-indigenous case area

BACKGROUND

Malaria cases in non-endemic zero-indigenous case areas are most likely to have been imported whatever of the route of importation. In countries recently declared malaria-free and now without local transmission, imported cases remain a threat to re-introduction of the disease and a burden on the health system.

CASE PRESENTATION

Three days after returning from a long trip to malaria- endemic countries; Abyei-Sudan, Chad and Uganda, a 41-year-old male resident from Jericho, Palestine, suffered paroxysms of fever, general fatigue, myalgia, arthralgia, headache, and a strong desire to vomit. Thin and thick Giemsa-stained blood smears were prepared and examined microscopically using oil immersion. Immature trophozoites (ring forms) were seen to parasitize approximately 10% of the erythrocytes revealing hyperparasitemia equivalent to > 100,000 parasites/ µl indicating severe malaria [1, 2]. The double chromatin configuration (headphones) and accolé (applique) position are both indicative of Plasmodium falciparum infection. The 18S rRNA- PCR targeting the rPLU6-rPLU5 region was used to confirm the diagnosis. The next-generation sequencing (NGS) method was carried out according to the manufacturer's instructions (Illumina® DNA Prep, (M) Tagmentation kit (20060060), Illumina) to identify Plasmodium spp. Furthermore, NGS produced a whole-genome sequence of 22.8Mbp of the 14 chromosomes and 25Kbp of the apicoplast. A BLAST search of the apicoplast DNA and selected chromosomal DNA revealed that P. falciparum was the causative agent. The merozoite surface protein-1 (msp-1) was used to construct a phylogenetic tree of 26 P. falciparum, including the one isolated from the patient from Jericho, which clustered with the Sudanese isolate indicating genetic relatedness between the two.

CONCLUSION

The travel history together with signs and symptoms of malaria, followed by prompt diagnosis using conventional microscopic inspection of Giemsa-stained films together with molecular DNA tracking tools like msp-1 were key means in tracking the place of origin of infection in the case of travel to multiple destination.

Transfusion-Transmitted Disorders 2023 with Special Attention to Bone Marrow Transplant Patients

Transfusion medicine is traditionally a strong/fundamental part of clinical practice, saving hundreds of millions of lives. However, blood-borne or transmitted infections are a well-known and feared possibility, a risk we relentlessly mitigate. Pathogens are continuously and rather quickly changing, so during the last decade, many, sometimes exotic, new pathogens and diseases were recorded and analyzed, and some of them were proved to be transmitted with transfusions. Blood or blood component transfusions are carried out after cautious preparative screening and inactivation maneuvers, but in some instances, newly recognized agents might escape from standard screening and inactivation procedures. Here, we try to focus on some of these proven or potentially pathogenic transfusion-transmitted agents, especially in immunocompromised patients or bone marrow transplantation settings. These pathogens are sometimes new challenges for preparative procedures, and there is a need for more recent, occasionally advanced, screening and inactivation methods to recognize and eliminate the threat a new or well-known pathogen can pose. Pathogen transmission is probably even more critical in hemophiliacs or bone marrow transplant recipients, who receive plasma-derived factor preparations or blood component transfusions regularly and in large quantities, sometimes in severely immunosuppressed conditions. Moreover, it may not be emphasized enough that transfusions and plasma-derived product administrations are essential to medical care. Therefore, blood-borne transmission needs continued alertness and efforts to attain optimal benefits with minimized hazards.

Nosocomial Malaria Transmissions Resolved by Genomic Analyses-A Retrospective Case Report Study in France: 2007-2021

BACKGROUND

Exposure of blood to malaria parasites can lead to infection even in the absence of the mosquito vector. During a stay in a healthcare facility, accidental inoculation of the skin with blood from a malaria patient might occur, referred to as nosocomial malaria.

METHODS

Between 2007 and 2021, we identified 6 autochthonous malaria cases that occurred in different French hospitals, originating from nosocomial transmission and imported malaria cases being the infection source. Four cases were observed during the coronavirus disease 2019 pandemic. The genetic relatedness between source and nosocomial infections was evaluated by genome-wide short tandem repeats (STRs) and single-nucleotide polymorphisms (SNPs).

RESULTS

None of the patients with autochthonous malaria had travel history to an endemic area nor had been transfused. For each case, both the source and recipient patients stayed a few hours in the same ward. After diagnosis, autochthonous cases were treated with antimalarials and all recovered except 1. Genetically, each pair of matched source/nosocomial parasite infections showed <1% of different STRs and <6.9% (<1.5% for monoclonal infections) of different SNPs. Similar levels of genetic differences were obtained for parasite DNA samples that were independently sequenced twice as references of identical infections. Parasite phylogenomics were consistent with travel information reported by the source patients.

CONCLUSIONS

Our study demonstrates that genomics analyses may resolve nosocomial malaria transmissions, despite the uncertainty regarding the modes of contamination. Nosocomial transmission of potentially life-threatening parasites should be taken into consideration in settings or occasions where compliance with universal precautions is not rigorous.

Epidemiological investigation of a case of malaria in a non-endemic area, Campo de Gibraltar, Cadiz, Spain, January 2022

We describe a non-imported malaria case reported in January 2022 in Campo de Gibraltar and the investigations by local public health authorities to identify the transmission mechanism and subsequent measures to prevent local transmission. Vector transmission, parenteral transmission, airport malaria, and imported malaria were ruled out. No clear mechanism of transmission was identified. The most probable cause was a hospital-acquired infection since the case was admitted to hospital at the same time as a case of imported Plasmodium falciparum malaria.

Usefulness of a commercial LAMP assay for detection of malaria infection, including Plasmodium knowlesi cases, in returning travelers in Spain

Objective

Main malaria diagnosis is based on microscopic examination combined with rapid diagnostic tests. Both methods have low sensitivity and specificity. Loop-mediated isothermal amplification techniques have shown a sensitivity similar to PCR but with lower times of performance. This study aimed to assess a commercial LAMP for the diagnosis of malaria (Alethia® Malaria) against the Nested-Multiplex-Malaria PCR, including the analytical sensitivity and the operational characteristics.

Results

One hundred five samples out of 114 rendered valid results, obtaining 85 positive samples and 18 negative samples with an agreement of 98% compared to the reference method with a sensitivity, specificity and kappa coefficient of 98.84%, 94.74% and 0.94 respectively, with only two discrepant samples. The turnaround time was estimated in 1 h and 30 min, with a cost of 32.67€ per determination. The results showed several advantages of the Alethia® Malaria, as it was easy to perform, minimal training requirement and 40 min run. Moreover, it includes an internal control to avoid false negatives. However, it also showed some limitations such as the need for a specific amplification and detection device, the detection of only Plasmodium spp. and a very high price.

Usefulness of Malachite-Green LAMP for Diagnosis of Plasmodium and Five Human Malaria Species in a Nonendemic Setting

Molecular methods are necessary to detect low-density malaria infections. The purpose of this study was to assess the diagnostic performance of six malachite-green loop-mediated amplification method (MG-LAMP) assays (MG-LAMP-Pf, MG-LAMP-Pv, MG-LAMP-Po, MG-LAMP-Pm, MG-LAMP-Pk, and MG-LAMP-Pspp) for the species-specific detection of each human Plasmodium, including P. knowlesi, and the Plasmodium genus compared with the nested-multiplex malaria polymerase chain reaction (NM-PCR), using 161 malaria-positive and 274 malaria-negative samples. MG-LAMP-Pspp assay detected the five human Plasmodium species and each species-specific MG-LAMP assay detected only its corresponding species. Sensitivity, specificity, and predictive values of MG-LAMP assays, compared with NM-PCR, were > 90%, except in the case of the MG-LAMP-Pm assay, which dropped to 47%. Limit of detection for MG-LAMP-Pspp assay ranged from 0.1 parasites/µL for P. falciparum to 16.9 parasites/µL for P. malariae samples, and it was similar for the rest of MG-LAMP assays except for the MG-LAMP-Pm assay. Turnaround time was estimated to be 2 hours and 35 minutes for one MG-LAMP assay and 4 hours and 15 minutes if all species-specific MG-LAMP is set up, whereas for the NM-PCR, turnaround time was ∼6 hours and 15 minutes. Costs per determination ranged from 1 to 6 euros for MG-LAMP assays and 5 euros for NM-PCR. Therefore, MG-LAMP assays appear to have good concordance compared with the reference method, except for the MG-LAMP-Pm assay. They can detect low parasitemia and identify malaria species, with lower costs and shorter time to obtain results, and they are suitable tools to be used in endemic and non-endemic countries for malaria detection.

Solidification of Self-Emulsifying Drug Delivery Systems as a Novel Approach to the Management of Uncomplicated Malaria

Malaria affects millions of people annually, especially in third-world countries. The mainstay of treatment is oral anti-malarial drugs and vaccination. An increase in resistant strains of malaria parasites to most of the current anti-malarial drugs adds to the global burden. Moreover, existing and new anti-malarial drugs are hampered by significantly poor aqueous solubility and low permeability, resulting in low oral bioavailability and patient noncompliance. Lipid formulations are commonly used to increase solubility and efficacy and decrease toxicity. The present review discusses the findings from studies focusing on specialised oral lipophilic drug delivery systems, including self-emulsifying drug delivery systems (SEDDSs). SEDDSs facilitate the spontaneous formation of liquid emulsions that effectively solubilise the incorporated drugs into the gastrointestinal tract and thereby improve the absorption of poorly-soluble anti-malaria drugs. However, traditional SEDDSs are normally in liquid dosage forms, which are delivered orally to the site of absorption, and are hampered by poor stability. This paper discusses novel solidification techniques that can easily and economically be up-scaled due to already existing industrial equipment that could be utilised. This method could, furthermore, improve product stability and patient compliance. The possible impact that solid oral SEDDSs can play in the fight against malaria is highlighted.

Diversity and distribution of larval habitats of mosquitoes (Diptera: Culicidae) in northern Spain: from urban to natural areas

Studies of the biodiversity of mosquito larval habitats are important for vector-borne disease control programs and help to improve vector distribution maps. This study was designed to investigate the geographical distribution of mosquito species and their larval habitats in urban, rural, and natural areas in northern Spain. Pre-imaginal stages were collected over two sampling periods (spring and summer) in 2019. In the laboratory, immature specimens were reared to the adult stage for species identification by morphological taxonomy and/or molecular methods. In total, 2,182 specimens belonging to 13 different native mosquito species of five genera were collected from 135 sampling points of which 59.2% harbored larvae. Culex pipiens s.l. was the most abundant species (45.1%), followed by Culex torrentium (12.3%), Anopheles maculipennis s.l. (10.2%), Culex hortensis (9.5%), and nine other species with lower frequencies that accounted for less than 25%. By molecular identification, An. maculipennis s.s. was identified as the only species within the An. maculipennis species complex and Cx. pipiens pipiens as the predominant subspecies of the Cx. pipiens species complex. Margins in large sunlit water bodies were the most suitable sites for An. maculipennis s.l., whereas Cx. pipiens s.l. was present in both natural and artificial habitats. The larval site index, species richness, and relative abundance of the mosquitoes were determined based on the characteristics of the sites where they were collected. The public health importance and ecology of some identified mosquitoes is also discussed.

High prevalence of malaria in a non-endemic setting among febrile episodes in travellers and migrants coming from endemic areas: a retrospective analysis of a 2013-2018 cohort

Background

The study aimed to analyse the likelihood of imported malaria in people with a suggestive clinical picture and its distinctive characteristics in a hospital in the south of Madrid, Spain.

Methods

Observational retrospective study that consisted of a review of all medical files of patients with any malaria test registered at Móstoles University Hospital between April 2013 and April 2018. All suspected malaria cases were confirmed by Plasmodium spp. polymerase chain reaction (PCR).

Results

Of the 328 patients with suspected malaria (53.7% migrant-travellers; 38.7% visitors; 7.6% travellers), 108 cases were confirmed (101 by Plasmodium falciparum), accounting for a 33% positive sample rate. Sixteen cases were diagnosed only by PCR. Patients with malaria, compared to those without, presented predominantly with fever (84% vs. 65%), were older (34 vs. 24 years), sought medical attention earlier (17d vs. 32d), had a greater number of previous malaria episodes (74% vs. 60%), lower levels of platelets (110,500µL vs. 250,000µL), and higher of bilirubin (0.6 mg/dL vs. 0.5 mg/dL). Severe malaria was present in 13 cases; no deaths were recorded. Malaria diagnosis showed a bimodal distribution with two peaks: June to September and November to January.

Conclusions

Malaria is still a common diagnosis among febrile patients coming from the tropics specially among migrant travellers. Fever, thrombocytopenia, and/or high bilirubin levels should raise suspicion for this parasitic infection. Prompt diagnosis is crucial to avoid severe cases and deaths.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03984-9.

Airport Malaria in Non-Endemic Areas: New Insights into Mosquito Vectors, Case Management and Major Challenges

Despite the implementation of preventive measures in airports and aircrafts, the risk of importing Plasmodium spp. infected mosquitoes is still present in malaria-free countries. Evidence suggests that mosquitoes have found a new alliance with the globalization of trade and climate change, leading to an upsurge of malaria parasite transmission around airports. The resulting locally acquired form of malaria is called Airport malaria. However, piecemeal information is available, regarding its epidemiological and entomological patterns, as well as the challenges in the diagnosis, treatment, and prevention. Understanding these issues is a critical step towards a better implementation of control strategies. To cross reference this information, we conducted a systematic review on 135 research articles published between 1969 (when the first cases of malaria in airports were reported) and 2020 (i.e., 51 years later). It appears that the risk of malaria transmission by local mosquito vectors in so called malaria-free countries is not zero; this risk is more likely to be fostered by infected vectors coming from endemic countries by air or by sea. Furthermore, there is ample evidence that airport malaria is increasing in these countries. From 2010 to 2020, the number of cases in Europe was 7.4 times higher than that recorded during the 2000-2009 decade. This increase may be associated with climate change, increased international trade, the decline of aircraft disinsection, as well as delays in case diagnosis and treatment. More critically, current interventions are weakened by biological and operational challenges, such as drug resistance in malaria parasites and vector resistance to insecticides, and logistic constraints. Therefore, there is a need to strengthen malaria prevention and treatment for people at risk of airport malaria, and implement a rigorous routine entomological and epidemiological surveillance in and around airports.

Imported Malaria in Portugal: Prevalence of Polymorphisms in the Anti-Malarial Drug Resistance Genes pfmdr1 and pfk13

Malaria is one of the ‘big three’ killer infectious diseases, alongside tuberculosis and HIV. In non-endemic areas, malaria may occur in travelers who have recently been to or visited endemic regions. The number of imported malaria cases in Portugal has increased in recent years, mostly due to the close relationship with the community of Portuguese language countries. Samples were collected from malaria-infected patients attending Centro Hospitalar Lisboa Ocidental (CHLO) or the outpatient clinic of Instituto de Higiene e Medicina Tropical (IHMT-NOVA) between March 2014 and May 2021. Molecular characterization of Plasmodium falciparum pfk13 and pfmdr1 genes was performed. We analyzed 232 imported malaria cases. The majority (68.53%) of the patients came from Angola and only three patients travelled to a non-African country; one to Brazil and two to Indonesia. P. falciparum was diagnosed in 81.47% of the cases, P. malariae in 7.33%, P. ovale 6.47% and 1.72% carried P. vivax. No mutations were detected in pfk13. Regarding pfmdr1, the wild-type haplotype (N86/Y184/D1246) was also the most prevalent (64.71%) and N86/184F/D1246 was detected in 26.47% of the cases. The typical imported malaria case was middle-aged male, traveling from Angola, infected with P. falciparum carrying wild type pfmdr1 and pfk13. Our study highlights the need for constant surveillance of malaria parasites imported into Portugal as an important pillar of public health.

An Ecologically Framed Comparison of The Potential for Zoonotic Transmission of Non-Human and Human-Infecting Species of Malaria Parasite

The threats, both real and perceived, surrounding the development of new and emerging infectious diseases of humans are of critical concern to public health and well-being. Among these risks is the potential for zoonotic transmission to humans of species of the malaria parasite, Plasmodium, that have been considered historically to infect exclusively non-human hosts. Recently observed shifts in the mode, transmission, and presentation of malaria among several species studied are evidenced by shared vectors, atypical symptoms, and novel host-seeking behavior. Collectively, these changes indicate the presence of environmental and ecological pressures that are likely to influence the dynamics of these parasite life cycles and physiological make-up. These may be further affected and amplified by such factors as increased urban development and accelerated rate of climate change. In particular, the extended host-seeking behavior of what were once considered non-human malaria species indicates the specialist niche of human malaria parasites is not a limiting factor that drives the success of blood-borne parasites. While zoonotic transmission of non-human malaria parasites is generally considered to not be possible for the vast majority of Plasmodium species, failure to consider the feasibility of its occurrence may lead to the emergence of a potentially life-threatening blood-borne disease of humans. Here, we argue that recent trends in behavior among what were hitherto considered to be non-human malaria parasites to infect humans call for a cross-disciplinary, ecologically-focused approach to understanding the complexities of the vertebrate host/mosquito vector/malaria parasite triangular relationship. This highlights a pressing need to conduct a multi-species investigation for which we recommend the construction of a database to determine ecological differences among all known Plasmodium species, vectors, and hosts. Closing this knowledge gap may help to inform alternative means of malaria prevention and control.

Mosquito fauna in Extremadura (western Spain): Updated catalog with new records, distribution maps, and medical relevance

An important element of vector control and surveillance of mosquito-borne diseases is updated information on vector species distribution. The aim of this study was to collect available information about mosquito species reported in Extremadura between 1920 and 2020 and create a catalog that would combine both published data and our recent field identifications. An exhaustive list is hereby presented, including species status and detailed distribution maps at a municipal level as well as their importance for public health. A total of 33 species, classified into five genera: Anopheles (five species), Aedes (14), Culex (nine), Culiseta (four), and Orthopodomyia (one) has been recorded, including 31 autochthonous, one invasive, Aedes (Stegomyia) albopictus, and one disappeared since 1953, Aedes (Stegomyia) aegypti. For the first time in Extremadura, we report the presence of important vectors such as Aedes (Aedimorphus) vexans vexans and Culex (Culex) perexiguus, and the new record of six species in the province of Badajoz, namely: Aedes (Dahliana) echinus, Aedes (Fredwardsius) vittatus, Aedes (Ochlerotatus) berlandi, Aedes (Ochlerotatus) pulcritarsis, Culex (Culex) mimeticus, and Culiseta (Culiseta) subochrea. Nineteen of these species are potential vectors of medical and veterinary relevance.

Suspect 'baggage canine heartworm' case: canine heartworm disease in a dog from Sydney, New South Wales

Locally acquired canine heartworm (Dirofilaria immitis) infection in the temperate southern climate zones of Australia is currently rare. We report a case of locally acquired canine heartworm from Sydney, New South Wales in a 12-year-old Fox Terrier × Jack Russell female that presented with coughing and breathing difficulties. Absence of heartworm prevention and no travel outside Sydney was noted. Blood sample was D. immitis positive using antigen test, but negative on Modified Knott's testing. PCR confirmed the presence of D. immitis DNA in circulating blood. Echocardiographic examination revealed multiple parallel echogenic lines separated by a hypoechoic region ('tram-tracks') in the right pulmonary artery. The patient was treated and clinical condition gradually improved over the following 12 months. Antigen test remained positive for D. immitis at ~7 months and became negative at ~15 months after the start of the treatment. The most plausible scenario is importation of infected mosquito(s) in the luggage arriving from Queensland, Australia, common holiday destination for many Sydney-siders. We consider this a case of 'baggage canine heartworm'. Canine heartworm in dogs who did not travel should be considered in the differential diagnosis and D. immitis antigen test coupled with Modified Knott's test or PCR must be considered.

Genome-Wide Scans for Ghanaian Plasmodium falciparum Genes Under Selection From Local and Chinese Host Populations

Initial malarial infection mostly causes symptomatic illness in humans. Infection that is not fatal induces complete protection from severe illness and death, and thus complete protection from severe illness or death is granted with sufficient exposure. However, malaria parasite immunity necessitates constant exposure. Therefore, it is important to evaluate lowered immunity and recurrent susceptibility to symptomatic disease in lower transmission areas. We aimed to investigate selection pressure based on transmission levels, antimalarial drug use, and environmental factors. We whole genome sequenced (WGS) P. falciparum clinical samples from Chinese hosts working in Ghana and compared the results with the WGS data of isolates from native Ghanaians downloaded from pf3k. The P. falciparum samples were generally clustered according to their geographic origin, and Chinese imported samples showed a clear African origin with a slightly different distribution from the native Ghanaian samples. Moreover, samples collected from two host populations showed evidence of differences in the intensity of selection. Compared with native Ghanaian samples, the China-imported isolates exhibited a higher proportion of monoclonal infections, and many genes associated with RBC invasion and immune evasion were found to be under less selection pressure. There was no significant difference in the selection of drug-resistance genes due to a similar artemisinin-based combination therapy medication profile. Local selection of malarial parasites is considered to be a result of differences in the host immunity or disparity in the transmission opportunities of the host. In China, most P. falciparum infections were imported from Africa, and under these circumstances, distinct local selective pressures may be caused by varying acquired immunity and transmission intensity. This study revealed the impact of host switching on the immune system, and it may provide a better understanding of the mechanisms that enable clinical immunity to malaria.

Environmental drivers, climate change and emergent diseases transmitted by mosquitoes and their vectors in southern Europe: A systematic review

Mosquito borne diseases are a group of infections that affect humans. Emerging or reemerging diseases are those that (re)occur in regions, groups or hosts that were previously free from these diseases: dengue virus; chikungunya virus; Zika virus; West Nile fever and malaria. In Europe, these infections are mostly imported; however, due to the presence of competent mosquitoes and the number of trips both to and from endemic areas, these pathogens are potentially emergent or re-emergent. Present and future climatic conditions, as well as meteorological, environmental and demographic aspects are risk factors for the distribution of different vectors and/or diseases. This review aimed to identify and analyze the existing literature on the transmission of mosquito borne diseases and those factors potentially affecting their transmission risk of them in six southern European countries with similar environmental conditions: Croatia, France, Greece, Italy, Portugal and Spain. In addition, we would identify those factors potentially affecting the (re)introduction or spread of mosquito vectors. This task has been undertaken with a focus on the environmental and climatic factors, including the effects of climate change. We undertook a systematic review of the vectors, diseases and their associations with climactic and environmental factors in European countries of the Mediterranean region. We followed the PRISMA guidelines and used explicit and systematic methods to identify, select and critically evaluate the studies which were relevant to the topic. We identified 1302 articles in the first search of the databases. Of those, 160 were selected for full-text review. The final data set included 61 articles published between 2000 and 2017.39.3% of the papers were related with dengue, chikungunya and Zika virus or their vectors. Temperature, precipitation and population density were key factors among others. 32.8% studied West Nile virus and its vectors, being temperature, precipitation and NDVI the most frequently used variables. Malaria have been studied in 23% of the articles, with temperature, precipitation and presence of water indexes as the most used variables. The number of publications focused on mosquito borne diseases is increasing in recent years, reflecting the increased interest in that diseases in southern European countries. Climatic and environmental variables are key factors on mosquitoes' distribution and to show the risk of emergence and/or spread of emergent diseases and to study the spatial changes in that distributions.

Two cases of airport-associated falciparum malaria in Frankfurt am Main, Germany, October 2019

Two cases of presumably airport-acquired falciparum malaria were diagnosed in Frankfurt in October 2019. They were associated with occupation at the airport, and Plasmodium falciparum parasites from their blood showed genetically identical microsatellite and allele patterns. Both had severe malaria. It took more than a week before the diagnosis was made. If symptoms are indicative and there is a plausible exposure, malaria should be considered even if patients have not travelled to an endemic area.

Several Plasmodium vivax relapses after correct primaquine treatment in a patient with impaired cytochrome P450 2D6 function

Background

Plasmodium vivax malaria is characterized by the presence of dormant liver-stage parasites, called hypnozoites, which can cause malaria relapses after an initial attack. Primaquine, which targets liver hypnozoites, must be used in combination with a schizonticidal agent to get the radical cure. However, relapses can sometimes occur in spite of correct treatment, due to different factors such as a diminished metabolization of primaquine.

Case presentation

In January 2019, a 21 years old woman with residence in Madrid, returning from a trip to Venezuela with clinical symptoms compatible with malaria infection, was diagnosed with vivax malaria. Chloroquine for 3 days plus primaquine for 14 days was the elected treatment. Two months later and after a second trip to Venezuela, the patient presented a second P. vivax infection, which was treated as the previous one. A third P. vivax malaria episode was diagnosed 2 months later, after returning from a trip to Morocco, receiving chloroquine for 3 days but increasing to 28 days the primaquine regimen, and with no more relapses after 6 months of follow up. The genotyping of P. vivax in the three malaria episodes revealed that the same strain was present in the different relapses. Upon confirmation of correct adherence to the treatment, non-description of resistance in the infection area and the highly unlikely re-infection on subsequent trips or stays in Spain, a possible metabolic failure was considered. CYP2D6 encodes the human cytochrome P450 isoenzyme 2D6 (CYP2D6), responsible for primaquine activation. The patient was found to have a CYP2D6*4/*1 genotype, which turns out in an intermediate metabolizer phenotype, which has been related to P. vivax relapses.

Conclusions

The impairment in CYP2D6 enzyme could be the most likely cause of P. vivax relapses in this patient. This highlights the importance of considering the analysis of CYP2D6 gene polymorphisms in cases of P. vivax relapses after a correct treatment and, especially, it should be considered in any study of dosage and duration of primaquine treatment.

The Importance of an Active Case Detection (ACD) Programme for Malaria among Migrants from Malaria Endemic Countries: The Greek Experience in a Receptive and Vulnerable Area

Greece has been malaria-free since 1974. In October 2011, following an outbreak of 36 locally acquired malaria (LAM) cases in Evrotas Municipality, a Pro-Active Case Detection (PACD) program for malaria was implemented among migrants from malaria-endemic countries, to support early diagnosis and treatment of cases. We evaluated the PACD program for the years 2012–2017 using indicators such as the number of locally acquired cases, the detection rate/sensitivity and the timeliness of diagnosis and treatment. We visited each migrant home every 7–15 days to screen migrants for malaria symptoms, performing Rapid Diagnostic Tests (RDTs) and blood smears on symptomatic patients. We estimated: (i) the number of malaria cases detected by the PACD, divided by the total number of reported malaria cases during the same period among the same population; (ii) the time between onset of symptoms, diagnosis and initiation of treatment. The total number of migrants who were screened for malaria symptoms for the years 2012–2017 was 5057 with 84,169 fever screenings conducted, while 2288 RDTs and 1736 blood smears were performed. During the same period, 53 imported P. vivax malaria cases were detected, while incidence of malaria among migrants was estimated at 1.8% annually. Ten and one LAM cases were also reported in 2012 and 2015, respectively. Sensitivity of PACD ranged from 86% to 100%; median timeliness between onset of symptoms and diagnosis decreased from 72 h in 2012 to 12 h in 2017 (83% decrease), while timeliness between diagnosis and treatment initiation was 0 h. The implementation of PACD could be considered an effective prevention and response tool against malaria re-introduction.

Non-imported malaria in Italy: paradigmatic approaches and public health implications following an unusual cluster of cases in 2017

BACKGROUND

The European region achieved interruption of malaria transmission during the 1970s. Since then, malaria control programs were replaced by surveillance systems in order to prevent possible re-emergence of this disease. Sporadic cases of non-imported malaria were recorded in several European countries in the past decade and locally transmitted outbreaks of Plasmodium vivax, most probably supported by Anopheles sacharovi, have been repeatedly reported from Greece since 2009. The possibility of locally-transmitted malaria has been extensively studied in Italy where the former malaria vector An. labranchiae survived the control campaign which led to malaria elimination. In this study, we present paradigmatic cases that occurred during a 2017 unusual cluster, which caused strong concern in public opinion and were carefully investigated after the implementation of the updated malaria surveillance system.

METHODS

For suspected locally-transmitted malaria cases, alerts to Ministry of Health (MoH) and the National Institute of Health (ISS) were mandated by the Local Health Services (LHS). Epidemiological investigations on the transmission modes and the identification of possible infection's source were carried out by LHS, MoH and ISS. Entomological investigations were implemented locally for all suspected locally-transmitted cases that occurred in periods suitable to anopheline activity. Molecular diagnosis by nested-PCR for the five human Plasmodium species was performed to support microscopic diagnosis. In addition, genotyping of P. falciparum isolate was carried out to investigate putative sources of infection and transmission modalities.

RESULTS

In 2017, a cluster of seven non-imported cases was recorded from August through October. Among them, P. ovale curtisi was responsible of one case whereas six cases were caused by P. falciparum. Two cases were proved to be nosocomial while the other five were recorded as cryptic at the end of epidemiological investigations.

CONCLUSIONS

The epidemiological evidence shows that the locally acquired events are sporadic, often remain unresolved and classified as cryptic ones despite investigative efforts. The "cluster" of seven non-imported cases that occurred in 2017 in different regions of Italy therefore represents a conscious alert that should lead us to maintain a constant level of surveillance in a former malaria endemic country.

Partitioning the influence of ecology across scales on parasite evolution

Vector-borne parasites must succeed at three scales to persist: they must proliferate within a host, establish in vectors, and transmit back to hosts. Ecology outside the host undergoes dramatic seasonal and human-induced changes, but predicting parasite evolutionary responses requires integrating their success across scales. We develop a novel, data-driven model to titrate the evolutionary impact of ecology at multiple scales on human malaria parasites. We investigate how parasites invest in transmission versus proliferation, a life-history trait that influences disease severity and spread. We find that transmission investment controls the pattern of host infectiousness over the course of infection: a trade-off emerges between early and late infectiousness, and the optimal resolution of that trade-off depends on ecology outside the host. An expanding epidemic favors rapid proliferation, and can overwhelm the evolutionary influence of host recovery rates and mosquito population dynamics. If transmission investment and recovery rate are positively correlated, then ecology outside the host imposes potent selection for aggressive parasite proliferation at the expense of transmission. Any association between transmission investment and recovery represents a key unknown, one that is likely to influence whether the evolutionary consequences of interventions are beneficial or costly for human health.

Prevalence of submicroscopic malaria infection in immigrants living in Spain

BACKGROUND

The importance of submicroscopic malaria infections in high-transmission areas could contribute to maintain the parasite cycle. Regarding non-endemic areas, its importance remains barely understood because parasitaemia in these afebrile patients is usually below the detection limits for microscopy, hence molecular techniques are often needed for its diagnosis. In addition to this, the lack of standardized protocols for the screening of submicroscopic malaria in immigrants from endemic areas may underestimate the infection with Plasmodium spp. The aim of this study was to assess the prevalence of submicroscopic malaria in afebrile immigrants living in a non-endemic area.

METHODS

A prospective, observational, multicentre study was conducted. Afebrile immigrants were included, microscopic observation of Giemsa-stained thin and thick blood smears, and two different molecular techniques detecting Plasmodium spp. were performed. Patients with submicroscopic malaria were defined as patients with negative blood smears and detection of DNA of Plasmodium spp. with one or both molecular techniques. Demographic, clinical, analytical and microbiological features were recorded and univariate analysis by subgroups was carried out with STATA v15.

RESULTS

A total of 244 afebrile immigrants were included in the study. Of them, 14 had a submicroscopic malaria infection, yielding a prevalence of 5.7% (95% confidence interval 3.45-9.40). In 71.4% of the positive PCR/negative microscopy cases, Plasmodium falciparum alone was the main detected species (10 out of the 14 patients) and in 4 cases (28.6%) Plasmodium vivax or Plasmodium ovale were detected. One patient had a mixed infection including three different species.

CONCLUSIONS

The prevalence of submicroscopic malaria in afebrile immigrants was similar to that previously described in Spain. Plasmodium vivax and P. ovale were detected in almost a third of the submicroscopic infections. Screening protocols for afebrile immigrants with molecular techniques could be useful for a proper management of these patients.

Imported cases of malaria in Spain: observational study using nationally reported statistics and surveillance data, 2002-2015

Background

Malaria was eliminated in Spain in 1964. Since then, more than 10,000 cases of malaria have been reported, mostly in travellers and migrants, making it the most frequently imported disease into this country. In order to improve knowledge on imported malaria cases characteristics, the two main malaria data sources were assessed: the national surveillance system and the hospital discharge database (CMBD).

Methods

Observational study using prospectively gathered surveillance data and CMBD records between 2002 and 2015. The average number of hospitalizations per year was calculated to assess temporal patterns. Socio-demographic, clinical and travel background information were analysed. Bivariate and multivariable statistical methods were employed to evaluate hospitalization risk, fatal outcome, continent of infection and chemoprophylaxis failure and their association with different factors.

Results

A total of 9513 malaria hospital discharges and 7421 reported malaria cases were identified. The number of reported cases was below the number of hospitalizations during the whole study period, with a steady increase trend in both databases since 2008. Males aged 25–44 were the most represented in both data sources. Most frequent related co-diagnoses were anaemia (20.2%) and thrombocytopaenia (15.4%). The risks of fatal outcome increased with age and were associated with the parasite species (Plasmodium falciparum). The main place of infection was Africa (88.9%), particularly Equatorial Guinea (33.2%). Most reported cases were visiting friends and relatives (VFRs) and immigrants (70.2%). A significant increased likelihood of hospitalization was observed for children under 10 years (aOR:2.7; 95% CI 1.9–3.9), those infected by Plasmodium vivax (4.3; 95% CI 2.1–8.7) and travellers VFRs (1.4; 95% CI 1.1–1.7). Only 4% of cases reported a correct regime of chemoprophylaxis. Being male, over 15 years, VFRs, migrant and born in an endemic country were associated to increased risk of failure in preventive chemotherapy.

Conclusions

The joint analysis of two data sources allowed for better characterization of imported malaria profile in Spain. Despite the availability of highly effective preventive measures, the preventable burden from malaria is high in Spain. Pre-travel advice and appropriately delivered preventive messages needs to be improved, particularly in migrants and VFRs.

Impact of recent and future climate change on vector-borne diseases

Climate change is one of the greatest threats to human health in the 21st century. Climate directly impacts health through climatic extremes, air quality, sea-level rise, and multifaceted influences on food production systems and water resources. Climate also affects infectious diseases, which have played a significant role in human history, impacting the rise and fall of civilizations and facilitating the conquest of new territories. Our review highlights significant regional changes in vector and pathogen distribution reported in temperate, peri-Arctic, Arctic, and tropical highland regions during recent decades, changes that have been anticipated by scientists worldwide. Further future changes are likely if we fail to mitigate and adapt to climate change. Many key factors affect the spread and severity of human diseases, including mobility of people, animals, and goods; control measures in place; availability of effective drugs; quality of public health services; human behavior; and political stability and conflicts. With drug and insecticide resistance on the rise, significant funding and research efforts must to be maintained to continue the battle against existing and emerging diseases, particularly those that are vector borne.

A systematic review of transfusion-transmitted malaria in non-endemic areas

BACKGROUND

Transfusion-transmitted malaria (TTM) is an accidental Plasmodium infection caused by whole blood or a blood component transfusion from a malaria infected donor to a recipient. Infected blood transfusions directly release malaria parasites in the recipient's bloodstream triggering the development of high risk complications, and potentially leading to a fatal outcome especially in individuals with no previous exposure to malaria or in immuno-compromised patients. A systematic review was conducted on TTM case reports in non-endemic areas to describe the epidemiological characteristics of blood donors and recipients.

METHODS

Relevant articles were retrieved from Pubmed, EMBASE, Scopus, and LILACS. From each selected study the following data were extracted: study area, gender and age of blood donor and recipient, blood component associated with TTM, Plasmodium species, malaria diagnostic method employed, blood donor screening method, incubation period between the infected transfusion and the onset of clinical symptoms in the recipient, time elapsed between the clinical symptoms and the diagnosis of malaria, infection outcome, country of origin of the blood donor and time of the last potential malaria exposure.

RESULTS

Plasmodium species were detected in 100 TTM case reports with a different frequency: 45% Plasmodium falciparum, 30% Plasmodium malariae, 16% Plasmodium vivax, 4% Plasmodium ovale, 2% Plasmodium knowlesi, 1% mixed infection P. falciparum/P. malariae. The majority of fatal outcomes (11/45) was caused by P. falciparum whilst the other fatalities occurred in individuals infected by P. malariae (2/30) and P. ovale (1/4). However, non P. falciparum fatalities were not attributed directly to malaria. The incubation time for all Plasmodium species TTM case reports was longer than what expected in natural infections. This difference was statistically significant for P. malariae (p = 0.006). A longer incubation time in the recipient together with a chronic infection at low parasite density of the donor makes P. malariae a subtle but not negligible risk for blood safety aside from P. falciparum.

CONCLUSIONS

TTM risk needs to be taken into account in order to enhance the safety of the blood supply chain from donors to recipients by means of appropriate diagnostic tools.