Investigations of the tick burden on passeriform, water-associated and predatory birds reveal new tick-host associations and habitat-related factors of tick infestation

BACKGROUND

Previous studies on the tick infestation of birds in the Carpathian Basin focused on songbirds (Passeriformes). Thus, the primary aim of the present work was to extend the scope of previous studies, i.e. to include aquatic (water-associated) bird species in a similar context, especially considering that these birds are usually long-distance migrants.

METHODS

Between March 2021 and August 2023, 11,919 birds representing 126 species were checked for the presence of ticks. From 352 birds belonging to 40 species, 905 ixodid ticks were collected. Tick species were identified morphologically and/or molecularly.

RESULTS

Ticks from avian hosts belonged to seven species: Ixodes ricinus (n = 448), I. frontalis (n = 31), I. festai (n = 2), I. arboricola (n = 36), I. lividus (n = 4), Haemaphysalis concinna (n = 382) and Dermacentor reticulatus (n = 2). Nymphs of I. ricinus occurred with a single activity peak around March-May, whereas its larvae typically infested birds in May, June or July. By contrast, H. concinna usually had its activity maximum during the summer (nymphs in June-July, larvae later in July-August). Interestingly, two ornithophilic species, I. frontalis and I. arboricola, were most active around winter months (between October and April). A significantly lower ratio of aquatic birds was found tick-infested than songbirds. Several new tick-host associations were revealed, including I. ricinus from Greylag Goose (Anser anser) and D. reticulatus from Great Egret (Ardea alba) and Sedge Warbler (Acrocephalus schoenobaenus). Ticks were collected for the first time in Europe from two species of predatory birds as well as from Little Bittern (Ixobrychus minutus). Bird species typically inhabiting reedbeds were most frequently infested with H. concinna, and most ticks localized at their throat, as opposed to forest-dwelling avian hosts, on which I. ricinus predominated and ticks were more evenly distributed.

CONCLUSIONS

In the evaluated region, aquatic birds appear to be less important in tick dispersal than songbirds. However, newly revealed tick-host associations in this category attest to their hitherto neglected contribution. The results suggest that the habitat type will have significant impact not only on the species composition but also on the feeding location of ticks on birds.

A single Haemoproteus plataleae haplotype is widespread in white ibis (Eudocimus albus) from urban and rural sites in southern Florida

The American white ibis (Eudocimus albus), a common bird species in Florida, has become increasingly urban, with many populations relying heavily on urban and suburban habitats, which may alter parasite transmission. Parasites of ibis, especially haemosporidians, are understudied. Avian haemosporidia can have a wide range of impacts on birds, including decreased reproductive success or increased mortality. Because southern Florida is subtropical and has a high diversity of potential vectors for haemosporidia, we hypothesized that there will be a high prevalence and genetic diversity of haemosporidia in white ibis. A total of 636 ibis from South Florida were sampled from 2010 to 2022, and blood samples were tested for haemosporidia by examination of Giemsa-stained thin blood smears and/or nested PCRs targeting the cytochrome b gene. A total of 400 (62.9%, 95% CI 59-66.7%) ibis were positive for parasites that were morphologically identified as Haemoproteus plataleae. Sequences of 302 positives revealed a single haplotype of Haemoproteus (EUDRUB01), which was previously reported from white ibis in South Florida and captive scarlet ibis (E. ruber) in Brazil. No Plasmodium or Leucocytozoon infections were detected. Parasitemias of the 400 positive birds were very low (average 0.084%, range 0.001%-2.16% [although only 2 birds had parasitemias >1%]). Prevalence and parasitemias were similar for males and females (68% vs. 61.6% and 0.081% vs. 0.071%, respectively). Prevalence in juveniles was lower compared with adults (52% vs. 67.4%) but parasitemias were higher in juveniles (0.117% vs. 0.065%). This data shows that H. plataleae is common in ibis in South Florida. Although parasitemias were generally low, additional research is needed to determine if this parasite has subclinical effects on ibis, if additional haplotypes or parasite species infect ibis in other regions of their range, or if H. plataleae is pathogenic for other sympatric avian species.

Spermiogenesis in the cattle egret (Bubulcus ibis)

Avian species comprise more than half of all vertebrates yet there is a dearth of information regarding spermatid development in this class of animals. This report of spermiogenesis in the cattle egret, Bubulcus ibis, is the first in the order Pelecaniformes. Five sexually mature and reproductively active male cattle egrets were captured in the wild, humanely euthanized, the reproductive organs dissected out, and tissues from the testes routinely prepared for transmission electron microscopy. Twelve steps of spermatid development, using the step-wise system, were determined. Acrosomogenesis in the egret results in a relatively short, solid, bullet-shaped acrosome that ends bluntly anteriorly and flat posteriorly or basally. The nucleus displays remarkable morphological changes, with the anterior end of the mature spermatid becoming flat, lacking a rostrum and an endonuclear canal. A perforatorium does not develop. It is noteworthy that a longitudinal, but not a circular, manchette develops during spermiogenesis in this bird. The proximal centriole is attached to the nucleus, at the implantation fossa, by means of well-formed, electron dense struts of material. An amorphous fibrous sheath develops in the principal piece. The interesting development and peculiar features of the acrosome and nucleus, as well as the absence of the perforatorium and circular manchette in the spermatozoon of the cattle egret, may be of phylogenetic significance.

Complete mitochondrial genome of Pelecanus crispus and its phylogeny

The Dalmatian Pelican (Pelecanus crispus), in the order Pelecaniformes, its habitat is distributed in Europe, Asia, and Africa. It is a large waterfowl that is of international concern. In this study, we first sequenced and described the complete mitochondrial genome and phylogeny of P. crispus. The results showed that the whole genome of P. crispus was 16,131 bp in length, and contained 13 protein-coding genes, 22 transfer RNA genes, two ribosome RNA genes, and one non-coding control region. The overall base composition of the mitochondrial DNA was 30.48% for A, 23.15% for T, 31.68% for C, and 14.69% for G, with a GC content of 46.37%. A phylogenetic tree of P. crispus in Pelecaniformes confirmed that P. crispus was sister to C. occidentalis. This information will be useful in the current understanding of the phylogeny and evolution of Pelecaniformes.

Using Bloodmeal Analysis to Assess Disease Risk to Wildlife at the New Northern Limit of a Mosquito Species

The historically southeastern mosquito species Culex erraticus has over the last 30 years undergone a marked expansion north. We evaluated this species' potential to participate in local disease cycles in the northeastern USA by identifying the vertebrate sources of blood in Cx. erraticus specimens from New Jersey. We found that the majority of bloodmeals (92.6%) were derived from birds, followed by 6.8% from mammals (of which half were human), and a single amphibian bloodmeal from a spring peeper (0.56%). Medium- and large-sized water birds from the order Pelecaniformes made up 60.4% of the bird species and 55.9% of all identified hosts. This group of birds is known enzootic hosts of arboviruses such as eastern equine encephalitis virus, for which Cx. erraticus is a competent vector. Additionally, we screened blooded mosquitoes for avian malaria parasites and identified three different lineages of Plasmodium, including what may represent a new Plasmodium species (likely a wetland bird specialist) in bloodmeals from Green Herons, a Great Egret, and a Double-Crested Cormorant. Our results support the utility of mosquito bloodmeals as sources of information about circulating wildlife pathogens and reveal the potential of range-expanding species to intensify local zoonoses and bridge enzootic pathogens to humans.

The complete mitochondrial genome of Pelecanus occidentalis (Pelecaniformes: Pelecanidae) and its phylogenetic analysis

Pelecanus occidentalis, in the order Pelecaniformes, is one of the most abundant and widespread waterbird species in the coast of America. However, the phylogenetic relationships among Pelecaniformes, Suliformes, and Ciconiiformes remain unresolved, particularly in Pelecanidae and Ciconiidae. In this study, we first sequenced and described the complete mitochondrial genome and phylogeny of P. occidentalis. The whole genome of P. occidentalis was 17,315 bp in length, and contained 13 protein-coding genes, 21 transfer RNA genes, two ribosome RNA genes, and one non-coding control region. The overall base composition of the mitochondrial DNA was 30.1% for A, 23.7% for T, 31.5% for C, and 14.6% for G, with a GC content of 46.1%. A phylogenetic tree confirmed that P. occidentalis (Pelecaniformes) was sister to C. boyciana (Ciconiiformes), and Ardeidae and Threskiornithidae were both monophyletic group. This information will be useful in the current understanding of the phylogeny and evolution of Pelecaniformes.