Gastrointestinal Helminths of Suliformes Birds from the Southern Coast of São Paulo, Brazil

Abstract

Seabirds of the families Fregatidae, Phalacrocoracidae and Sulidae, common on the southeastern coast of Brazil, form colonies and play a bioindicator role in coastal ecosystems due to their ecological habits. This study aimed to identify the prevalence of parasitic helminths in Suliformes birds, of the species Fregata magnificens Mathews, 1914, Sula leucogaster Boddaert, 1783 and Nannopterum um Gmelin, 1789, from the Instituto de Pesquisas Cananeia (IPeC) on the southern coast of the State of São Paulo, and to record the diversity and parasitic indices, since reports of helminth prevalence in pelagic birds are scarce in Brazil. From 2018 to 2020, a total of 270 nematode specimens and 271 acanthocephalan parasites were collected from 51 Suliformes birds (20 F. magnificens, 10 N. brasilianum and 21 S. leucogaster). The host species F. magnificens was parasitized by Contracaecum plagiaticium and Contracaecum pelagicum. The host S. leucogaster was parasitized by C. plagiaticium. In the host N. brasilianum, specimens of Contracaecum australe, Contracaecum rudolphii, Contracaecum multipapillatum, Syncuaria squamata and Andracantha tandemtesticulata were found. This is the first report of C. plagiaticium and C. pelagicum in F. magnificens in Brazilian territory, and of A. tandemtesticulata in N. brasilianum in the southeast region of Brazil.

1. Introduction

The Brazilian fauna is one of the most important in the world in terms of biodiversity [1]. Among the various bird species in the country, those with coastal and marine habits exhibit great biological and ecological importance, as they serve as bioindicators of their habitats [2]. Pelagic birds require habitats rich in nutrients and a high diversity of prey for their development [3], feeding mainly on fish and crustaceans, but also being able to supplement their diet with amphibians and mollusks [4].

The Order Suliformes comprises four families, two of which are exclusively marine birds (Fregatidae and Sulidae), while the other two contain aquatic species that prefer freshwater but may occasionally inhabit coastal areas with brackish or saltwater environments, such as estuaries, bays and mangroves (Phalacrocoracidae and Anhingidae) [5,6]. The main representatives of these families in Brazilian territory are the birds Fregata magnificens Mathews, 1914, Sula leucogaster Reichenbach, 1849, Nannopterum brasilianum Gmelin, 1789 (=Phalacrocorax brasilianus) and Anhinga anhinga [6].

Marine and aquatic birds predominantly gather in colonies during reproductive seasons. Gregarious behavior is crucial for individual interactions and collective protection among birds. However, colonial aggregation may present significant disadvantages for these animals. The proximity between animals, both conspecific and heterospecific, makes individuals susceptible to the spread of infectious and parasitic agents [3,7,8].

Although crucial, parasitological studies on Brazilian marine birds remain scarce and insufficient to adequately characterize their parasitic fauna. Most research focuses on species with zoonotic potential, creating a knowledge gap regarding other taxa. While punctual records of helminths in Suliformes birds exist in Brazil [9,10,11,12,13,14], comprehensive studies addressing parasitic diversity and host–parasite relationships in these groups are urgently needed.

Understanding diseases and host–parasite relationships in Brazilian avian species is crucial for ensuring the survival and effectiveness of conservation and rehabilitation programs, both for birds and their ecosystems. This study aims to identify helminths collected from three Suliformes species—S. leucogaster, F. magnificens and N. brasilianum—along the southern coast of São Paulo State, Brazil, through morphological and morphometric analysis, and to present their parasitic indices.

2. Materials and Methods

Between 2018 and 2020, researchers from the Instituto de Pesquisas Cananéia (IPeC) collected 51 deceased Suliformes specimens along the coastal beaches of southern São Paulo State, Brazil, comprising 20 F. magnificens, 10 N. brasilianum and 21 S. leucogaster.

At the IPeC, the birds underwent necropsy, where parasitic helminths were collected, preserved in 70% ethanol and sent for analysis. Among the collected helminths, some were identified as nematodes and acanthocephalans, while others consisted of digenean trematode and cestode fragments that were not in suitable condition for identification.

Following collection, helminths were fixed, preserved in 70% ethanol and processed according to Knoff & Gomes (2012) [15]. Nematodes were cleared in Amann’s lactophenol and subsequently preserved in 70% ethanol. Taxonomic classification followed De Ley & Blaxter (2002) [16], with specific identification using Wong et al. (1986) [17], Vicente et al. (1995, 1996) [9,18], Monteiro et al. (2006) [11] and Garbin et al. (2011) [19]. Acanthocephalans were stained with Langeron’s carmine and mounted on slides with Canada balsam. Specimens were identified following Monteiro et al. (2006) [12] and taxonomically classified according to Amin (2013) [20]. Parasitological indices (prevalence and mean intensity) for the recovered helminth species were calculated following Bush et al. (1997) [21], with infection ranges reported accordingly.

This study was approved by the Comitê de Ética no Uso de Animais (CEUA) of Universidade Federal Fluminense (Protocol No.9454060618) and by the Sistema de Autorização e Informação em Biodiversidade (Sisbio) under the Scientific Activities Permit No.63356-1 (Authentication Code: 11556589).

3. Results

A total of 51 marine birds comprising 3 species (21 Sula leucogaster, 20 Fregata magnificens and 10 Nannopterum brasilianum) collected along the southeastern Brazilian coast by the Cananéia Research Institute were examined. Parasitological analysis revealed a diverse helminth fauna, with nematodes of the genus Contracaecum being predominant.

Helminths of the genus Contracaecum exhibit lips without rows of teeth and well-developed interlabia. Males present pre- and post-cloacal papillae, and two long spicules that are equal or nearly equal in length. Females are oviparous and have a vulva located in the anterior region of the body [9].

The main morphological characteristic used to differentiate species is the length of the male spicules. The spicules of C. plagiaticium range from 2.8 to 3.36 mm in length, those of C. pelagicum from 4.10 to 4.75 mm, those of C. multipapillatum from 0.91 to 1.19 mm and those of C. rudolphii from 7.8 to 8.4 mm [9,18]. Garbin et al. (2011) [19] reported in their description of C. australe that its spicules reach nearly half the total body length, measuring approximately 13.20 mm.

Syncaria spp. are parasites of aquatic birds; S. squamata is a medium-sized nematode with a white coloration and marked sexual dimorphism. Cordons originating dorsally and ventrally to pseudolabia, anastomising laterally. Vulva and anus are located in the posterior end, tail conical. Females measure between 20.6 and 30.0 mm in length, 0.58 to 0.76 mm in width and have narrow cordons measuring 1.0 to 1.4 mm in length. Measurements are according to Monteiro et al. (2006) [11].

Among 21 examined S. leucogaster specimens, 4 were parasitized (19% prevalence), yielding 7 helminths total. These included four adult Contracaecum plagiaticium Lent & Freitas, 1948 and three Contracaecum sp. larvae, all localized in the host stomachs. Mean infection intensity was 1.75 helminths per infected bird (range: 1–2 parasites/host). Complete morphometric data are presented in

Table 1. Morphometric data of Contracaecum plagiaticium parasite of Sula leucogaster.

Parameters	C. plagiaticium Male	C. plagiaticium Female
Total Length (mm)—Range	16.54–17.74	21.66–31.60
Total Length (mm)—Mean	17.14	26.63
Total Width (mm)—Range	0.51–0.65	0.65–1.26
Total Width (mm)—Mean	0.58	0.95
Spicules (mm)—Range	4.09–4.27	-
Spicules (mm)—Mean	4.18	-
Eggs (mm)—Range	-	0.048
Eggs (mm)—Mean	-	0.048
Vulva–Anterior End Distance (mm)—Range	-	6.86–15.69
Vulva–Anterior End Distance (mm)—Mean	-	11.27
Anus–Caudal Apex Distance (mm)—Range	-	0.37–0.47
Anus–Caudal Apex Distance (mm)—Mean	-	0.42

. Larval identification was restricted to the genus level due to either absent adult specimens or suboptimal preservation state.

In Fregata magnificens, parasites were detected in 4 of 20 examined birds (20% prevalence). Hosts harbored 76 Contracaecum plagiaticium specimens in the stomach (Figure 1A,B), showing a 15% infection prevalence, with intensities ranging from 1 to 55 helminths (mean: 25.3 parasites/infected bird). In the intestine of one bird, two Contracaecum pelagicum Johnston & Mawson, 1942 (Figure 2A) specimens were found (5% prevalence; mean intensity: two parasites/infected host). Detailed morphometric data are provided in

Table 2. Morphometric data of the species of the genus Contracaecum parasites of Fregata magnificens.

Parameters	C. plagiaticium Male	C. plagiaticium Female	C. pelagicum Male	C. pelagicum Female
Total Length (mm)—Range	14.80–19.90	16.84–30.15	-	36.0
Total Length (mm)—Mean	17.31	21.03	-	-
Total Width (mm)—Range	0.47–1.05	0.56–1.69	-	1.33
Total Width (mm)—Mean	0.67	1.03	-	-
Spicules (mm)—Range	2.04–3.80	-	-	-
Spicules (mm)—Mean	3.03	-	-	-
Eggs (mm)—Range	-	0.048–0.057	-	-
Eggs (mm)—Mean	-	0.050	-	-
Vulva–Anterior End Distance (mm)—Range	-	10.10–16.68	-	9.28
Vulva–Anterior End Distance (mm)—Mean	-	12.01	-	-
Anus–Caudal Apex Distance (mm)—Range	-	0.28–0.32	-	0.30
Anus–Caudal Apex Distance (mm)—Mean	-	0.29	-	-

.

Nannopterum brasilianum exhibited a 90% infection prevalence (9/10 examined birds). Stomach contents revealed the following four nematode species: Contracaecum australe Garbin, Mattiucci, Paoletti, González-Acuña & Nascetti, 2011 (Figure 1C), Contracaecum rudolphii Hartwich, 1964 (Figure 2D), Contracaecum multipapillatum (von Drasche, 1882) Lucker, 1941 (Figure 2E) and Syncuaria squamata (Linstow, 1883) Wong, Anderson & Bartlett, 1986 (Figure 3). One host’s intestine contained the acanthocephalan Andracantha tandemtesticulata Monteiro, Amato & Amato, 2006 (Figure 4). Coinfections occurred in four birds: two with concurrent C. australe and S. squamata infections, one with C. rudolphii and S. squamata, and one with C. rudolphii and C. multipapillatum. Complete parasitological indices are presented in

Table 3. Parasitological indices of helminth parasites of Nannopterum brasilianum.

Species	Prevalence	Range of Infection	Mean Intensity/Intensity
Contracaecum australe	40%	19–33	24
Contracaecum rudolphii	50%	4–32	14.4
Contracaecum multipapillatum	10%	-	1
Syncuaria squamata	30%	5–6	5.3
Andracantha tandemtesticulata	10%	-	271

. Genus-specific morphometric data are detailed in

Table 4. Morphometric data of the species of the genus Contracaecum parasites of Nannopterum brasilianum.

Parameters	C. australe Male	C. australe Female	C. rudolphii Male	C. rudolphii Female	C. multipapillatum Male
Total Length (mm)—Range	13.20–26.27	18.80–46.36	11.04–19.74	15.27–36.66	12.52
Total Length (mm)—Mean	19.43	26.53	16.46	24.50	-
Total Width (mm)—Range	0.51–0.94	0.58–1.17	0.30–0.82	0.61–1.31	0.50
Total Width (mm)—Mean	0.75	0.91	0.62	0.94	-
Spicules (mm)—Range	7.87–16.88	-	8.27–11.58	-	1.18
Spicules (mm)—Mean	13.22	-	9.81	-	-
Eggs (mm)—Range	-	0.048	-	0.048	-
Eggs (mm)—Mean	-	0.048	-	0.048	-
Vulva–Anterior End Distance (mm)—Range	-	5.28–11.15	-	5.87–10.81	-
Vulva–Anterior End Distance (mm)—Mean	-	7.93	-	8.09	-
Anus–Caudal Apex Distance (mm)—Range	-	0.19–0.37	-	0.11–0.35	-
Anus–Caudal Apex Distance (mm)—Mean	-	0.33	-	0.28	-

,

Table 5. Measurements of Syncuaria squamata parasite of Nannopterum brasilianum.

Parameters	S. squamata Female
Total Length (mm)—Range	21.15–27.49
Total Length (mm)—Mean	23.89
Total Width (mm)—Range	0.47–0.70
Total Width (mm)—Mean	0.63
Cordon Length (mm)—Range	0.82–1.20
Cordon Length (mm)—Mean	0.98
Cordon Width (mm)—Range	0.28–0.58
Cordon Width (mm)—Mean	0.38
Eggs (mm)—Range	0.028 × 0.019
Eggs (mm)—Mean	0.028 × 0.019
Anus–Caudal Apex Distance (mm)—Range	0.07–0.09
Anus–Caudal Apex Distance (mm)—Mean	0.09
Vulva–Caudal Apex Distance (mm)—Range	0.28–0.30
Vulva–Caudal Apex Distance (mm)—Mean	0.28

and

Table 6. Morphometric data of Andracantha tandemtesticulata parasite of Nannopterum brasilianum.

Parameters	A. tandemtesticulata Male
Total Length (mm)—Range	1.65–5.05
Total Length (mm)—Mean	3.59
Total Width (mm)—Range	0.47–0.98
Total Width (mm)—Mean	0.83
Proboscis Length (mm)—Range	0.45–0.63
Proboscis Length (mm)—Mean	0.52
Proboscis Width (mm)—Range	0.12–0.19
Proboscis Width (mm)—Mean	0.16

. Nannopterum brasilianum demonstrated the highest parasitic diversity and infection intensity among studied hosts.

Representative specimens of each helminth species were deposited in the Helminthological Collection of the Oswaldo Cruz Institute (CHIOC) under the following accession numbers: Syncuaria squamata (39685), Contracaecum rudolphii (39686), Contracaecum australe (39687–39688), Contracaecum plagiaticium (39689), Contracaecum pelagicum (39690) and Andracantha tandemtesticulata (40461–40462).

4. Discussion

Within the Sulidae family, Sula leucogaster (commonly called brown booby) predominates along southeastern Brazil’s coastline [6]. These birds typically form breeding colonies on nearshore islands. Their piscivorous diet primarily includes fish from the Sciaenidae Family, like Paralonchurus brasiliensis and Micropogonias furnieri, known intermediate hosts for Contracaecum sp. larvae [22,23].

The first record of C. plagiaticium in S. leucogaster was documented by Vicente et al. (1996) [18] from gastrointestinal tract material collected in Rio de Janeiro State, Brazil. Subsequently, C. pelagicum was reported in this host species by Silva et al. (2005) [24] during biological studies in São Paulo State, Brazil.

In the present study, few C. plagiaticium specimens from S. leucogaster carcasses were recovered, including three larval-stage individuals, suggesting recent host infection. As highly mobile seabirds, brown boobies can spend months foraging pelagically on fish with lower parasite loads, due to reduced exposure to human-impacted coastal areas and dense animal colonies. Conversely, fish from coastal zones near ports or nesting colonies show higher larval infection rates, as habitat contamination by infected bird feces perpetuates parasite life cycles [25].

Within the Fregatidae family, Fregata magnificens represents the most abundant species along the Brazilian coast. These birds nest exclusively on oceanic and coastal islands [26] and exhibit crepuscular colony formation with high population densities [2]. This behavioral pattern likely facilitates parasite transmission among colony members.

The existing studies of this bird species are primarily focused on its ecological aspects [27]. This reflects the need for further investigation of the parasitic fauna of this host, particularly in Brazil, where they are commonly observed in natural environments [28].

Branco et al. (2007) [29] reported that the fish species Paralonchurus brasiliensis and Micropogonias furnieri are part of the diet of frigatebirds in the state of Santa Catarina, Brazil, while Alves & Luque (2001) [22] and Luque et al. (2003) [23] observed Contracaecum larvae in the mesentery of these fish species along the coast of Rio de Janeiro State, Brazil. Thus, it is likely that the infection of F. magnificens by these parasites occurs due to its feeding habits.

In their review of parasitic nematodes in Brazilian birds, Vicente et al. (1996) [18] documented the presence of C. granulosum and Contracaecum sp. parasitizing F. magnificens in the state of Rio de Janeiro, Brazil.

This is the first report of infection of F. magnificens by C. plagiaticium and C. pelagicum. This occurrence may be associated with the shared piscivorous habits and ecological niches between frigatebirds from southeastern Brazil and brown boobies, which have previously been described as hosts of these parasites [18,24].

In Brazil, both parasite species have been reported in Spheniscus magellanicus Foster, 1781 along the coast of Rio de Janeiro [30]. Additionally, C. pelagicum has been recorded in a specimen of S. magellanicus from the state of Espírito Santo [31]. C. plagiaticium has also been identified as a parasite of Nycticorax nycticorax hoactli Gmelin, 1789 and Pilherodius pileatus Boddaert, 1783 in the states of Mato Grosso do Sul and Rio de Janeiro [32].

The Phalacrocoracidae family comprises cormorants and shags distributed across coastal regions worldwide, except in Arctic areas. In Brazil, the only representative is Nannopterum brasilianum Gmelin, 1789 (syn. Phalacrocorax brasilianus), locally known as the Neotropic cormorant or ‘Biguá’ [6]. This species shows a preference for freshwater environments, typically inhabiting riverbanks and lakeshores, though it occasionally occupies coastal marine environments [5]. It does not exhibit migratory behavior [3] and forms colonies along rivers and lakes [5], which facilitates the susceptibility to helminth transmission among individuals.

The fishes Paralonchurus brasiliensis and Micropogonias furnieri constitute key dietary components of Neotropic cormorants in southern Brazil [33]. These fish species serve as intermediate hosts for Contracaecum spp. [22,23]. Vicente et al. (1996) [18] recognized the cormorant as a definitive host of C. spiculigerum (=C. rudolphii). The first report of C. rudolphii parasitizing cormorants in Brazil was by Amato et al. (2006) [10], following an earlier report of this parasite in Chilean cormorants by Torres et al. (2005) [34]. Carvalho et al. (2024) [13] documented N. brasilianum infections by C. rudolphii, C. australe, C. multipapillatum, Syncuaria squamata and Andracantha sp., including the first Brazilian records of C. australe and C. multipapillatum in this host. The species composition and infection prevalence observed in that study are similar to our findings, suggesting that these helminths are common parasites of N. brasilianum in Brazilian coast.

A coinfection of C. rudolphii and C. multipapillatum in Phalacrocorax auritus Lesson, 1831 was reported in Florida, USA [35]; C. rudolphii and C. septentrionale Kreis, 1955 were in coinfection in the proventriculus of Phalacrocorax aristotelis aristotelis Linnaeus, 1761 in the southeastern North Atlantic [36]. In Iraq, Phalacrocorax carbo Linnaeus, 1758 was found to be infected by C. rudolphii, and Al-Moussawi (2017) [37] provided detailed descriptions of lip structures, interlabia, caudal papillae and the shape of the spicule tip using scanning electron microscopy (SEM).

The species C. australe was first described as a parasite of N. brasilianum in Chile, demonstrating its geographical distribution along both coastal regions of South America [19].

The present study also revealed infection prevalence rates consistent with Monteiro et al. (2006a) [11], who first reported S. squamata parasitism in Neotropic cormorants in Brazil.

The infection of these birds by helminths of the genus Andracantha is consistent with the description of a new species of acanthocephalan by Monteiro et al. (2006b) [12], which was named A. tandemtesticulata due to the unique characteristic of males having testes arranged in tandem, rather than the parallel orientation typical of other species of this genus. The acanthocephalan specimens found in this study were morphometrically similar, both in size and in the tandem arrangement of the testes.

5. Conclusions

Given that helminth parasitism can compromise marine bird conservation and rehabilitation efforts, comprehensive documentation of histopathological alterations and health impacts in Brazilian pelagic avifauna is essential. Expanded studies are needed to fully characterize host–parasite relationships, between these birds and their helminths, in order to determine the full extent of their impact.

Helminth species identification in this study relied on morphometric analysis using light microscopy. However, molecular characterization remains essential to establish the genetic profiles of these parasites.

This is the first report of C. plagiaticium and C. pelagicum in F. magnificens in Brazilian territory, and of A. tandemtesticulata in N. brasilianum in the southeast region of Brazil.

Characterizing helminth–host relationships in seabirds is fundamental for the success of conservation programs and for the determination of parasite species present in Brazil. As the country harbors one of the world’s highest number of threatened avian species, understanding all of the potential health threats, including parasitic diseases, becomes essential for effective species protection.