Human and animal dirofilariasis: the emergence of a zoonotic mosaic.

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Clinical, microbiological, and molecular characterization of pediatric invasive infections by Streptococcus pyogenes in Spain in a context of global outbreak.

In December 2022, an alert was published in the UK and other European countries reporting an unusual increase in the incidence of Streptococcus pyogenes infections. Our aim was to describe the clinical, microbiological, and molecular characteristics of group A Streptococcus invasive infections (iGAS) in children prospectively recruited in Spain (September 2022-March 2023), and compare invasive strains with strains causing mild infections. One hundred thirty isolates of S. pyogenes causing infection (102 iGAS and 28 mild infections) were included in the microbiological study: emm typing, antimicrobial susceptibility testing, and sequencing for core genome multilocus sequence typing (cgMLST), resistome, and virulome analysis. Clinical data were available from 93 cases and 21 controls. Pneumonia was the most frequent clinical syndrome (41/93; 44.1%), followed by deep tissue abscesses (23/93; 24.7%), and osteoarticular infections (11/93; 11.8%). Forty-six of 93 cases (49.5%) required admission to the pediatric intensive care unit. iGAS isolates mainly belonged to emm1 and emm12; emm12 predominated in 2022 but was surpassed by emm1 in 2023. Spread of M1UK sublineage (28/64 M1 isolates) was communicated for the first time in Spain, but it did not replace the still predominant sublineage M1global (36/64). Furthermore, a difference in emm types compared with the mild cases was observed with predominance of emm1, but also important representativeness of emm12 and emm89 isolates. Pneumonia, the most frequent and severe iGAS diagnosed, was associated with the speA gene, while the ssa superantigen was associated with milder cases. iGAS isolates were mainly susceptible to antimicrobials. cgMLST showed five major clusters: ST28-ST1357/emm1, ST36-ST425/emm12, ST242/emm12.37, ST39/emm4, and ST101-ST1295/emm89 isolates. IMPORTANCE: Group A Streptococcus (GAS) is a common bacterial pathogen in the pediatric population. In the last months of 2022, an unusual increase in GAS infections was detected in various countries. Certain strains were overrepresented, although the cause of this raise is not clear. In Spain, a significant increase in mild and severe cases was also observed; this study evaluates the clinical characteristics and the strains involved in both scenarios. Our study showed that the increase in incidence did not correlate with an increase in resistance or with an emm types shift. However, there seemed to be a rise in severity, partly related to a greater rate of pneumonia cases. These findings suggest a general increase in iGAS that highlights the need for surveillance. The introduction of whole genome sequencing in the diagnosis and surveillance of iGAS may improve the understanding of antibiotic resistance, virulence, and clones, facilitating its control and personalized treatment.

Canine dirofilariosis caused by Dirofilaria immitis is a risk factor for the human population on the island of Gran Canaria, Canary Islands, Spain.

The aim of the present study was compare the prevalence of D. immitis in dogs and seroprevalence in humans of Gran Canaria (Canary Islands, Spain) taking into consideration the four isoclimatic areas of the island. A close relationship between the prevalence of Dirofilaria immitis in dogs and the seroprevalence in humans, in each isoclimatic area, was observed. The highest seroprevalence of infection in both canine and human hosts were found in a strip of mid-range altitude with 25.47% and 30.4% in dogs and 25.66% and 29.73% in humans, respectively. The coastal zone and the highest part of the island have prevalences significantly lower. These results demonstrate that the risk of infection by D. immitis in the human population in each area is tied to the prevalence in the canine population. Physicians should be alerted to the possibility of finding cases of human pulmonary dirofilariosis amongst the inhabitants of the island.

Excretory/secretory antigens from Dirofilaria immitis adult worms interact with the host fibrinolytic system involving the vascular endothelium.

Dirofilaria immitis is the causative agent of canine and feline heartworm disease. The parasite can survive for long periods of time (7 years or more) in the circulatory system of immunocompetent reservoirs, producing usually a chronic inflammatory vascular disease. In addition, the simultaneous death of groups of adult worms can trigger an acute disease characterized by the exacerbation of inflammatory reactions and the emergence of serious thromboembolic events. In the context of the D. immitis/host relationships, the aim of this study was to investigate the interaction between the excretory/secretory antigens from D. immitis adult worms (DiES) and the fibrinolytic system of the host. Using an enzyme-linked immunosorbent assay we showed that DiES extract is able to bind plasminogen and generate plasmin, although this fact requires the presence of the tissue plasminogen activator (t-PA). Moreover, we established that DiES extract enhances t-PA expression in cultured vascular endothelial cells. Additionally, 10 plasminogen-binding proteins from DiES extract were identified by mass spectrometry (HSP60, actin-1/3, actin, actin 4, transglutaminase, GAPDH, Ov87, LOAG_14743, galectin and P22U). The data suggest that DiES antigens interact with the environment of the parasite regulating the activation of the fibrinolytic system of the host with involvement of the vascular endothelium in the process.