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. 2025 Aug 8;124(8):90. doi: 10.1007/s00436-025-08542-9

Outcome of parasitological examinations in cats in Germany: a retrospective survey

Jacqueline Csokai 1,✉, Michaela Gentil 2, Anton Heusinger 2, Elisabeth Müller 2
PMCID: PMC12334491  PMID: 40779070

Abstract

This retrospective study examined the occurrence of endoparasites in feline faecal samples in a German diagnostic laboratory between January 2019 and December 2019. Different methods for endoparasite detection were performed: 6,425 samples by flotation method as well as sodium acetate-acetic acid-formalin concentration (SAFC) technique, 721 samples by Baermann-Wetzel migration technique, 3,233 samples by a Giardia coproantigen enzyme-linked immunosorbent assay (ELISA), 346 samples by a Cryptosporidium coproantigen ELISA, 1,007 samples by polymerase chain reaction (PCR) testing for Giardia duodenalis, and 672 samples by PCR testing for Cryptosporidium spp. A total of 8.5% of the samples were positive for parasites in the microscopic examination using the flotation method and SAFC technique in combination: Toxocara cati (3.8%), Cystoisospora spp. (2.3%), Giardia duodenalis (1.9%), Ancylostomatidae (0.3%), lungworm larvae (0.3%), Toxoplasma gondii/Hammondia hammondi (0.2%), Taeniidae (0.2%), Capillaria spp. (0.2%), Toxascaris leonina (0.08%), Sarcocystis spp. (0.06%) and Dipylidium caninum (0.02%). The detection rate of lungworm larvae by the Baermann-Wetzel migration technique was 4.7%. Giardia duodenalis was detected by ELISA in 8.1% of the samples and by PCR in 7.9%. Detection rates for Cryptosporidium spp. were 1.7% by ELISA and 2.5% by PCR. Cats in the first year of life were more frequently infected with parasites than older animals.

Keywords: Cats, Endoparasites, Prevalence, Germany, ELISA, PCR

Introduction

In Germany, cats are popular pets that are kept exclusively indoors or are allowed to roam free as well. Hunting and eating their prey, outdoor cats have a higher risk of acquiring parasite infection (Strube et al. 2019). The prevention or rapid control of an infection with endoparasites in cats is of concern due to two points. Firstly, some endoparasites can cause clinical symptoms in cats, and secondly some parasites have zoonotic potential.

Endoparasites that are more pathogenic for cats include Toxocara spp., Ancylostoma tubaeforme, Cystoisospora spp. and Giardia duodenalis, which can cause symptoms such as diarrhoea, weight loss, inappetence and apathy and especially affect kittens and young animals. Another important endoparasite, Aelurostrongylus abstrusus, parasitises in the lower respiratory tract and can cause cough, dyspnoea, tachypnoea, openmouth breathing, wheezing, nasal discharge, sneezing, lethargy and weight loss. Fatal cases can occur (Epe 2009; Payne and Artzer 2009; Epe et al. 2010; Traversa 2012; Dubey 2018; Jimenez Castro and Sapp 2020; Morelli et al. 2021).

Endoparasites of cats which can infect humans include Toxoplasma gondii, T. cati, G. duodenalis, Echinococcus multilocularis and Dipylidium caninum (Feng and Xiao 2011; ESCCAP 2014). Human toxoplasmosis is a common parasitic zoonosis that is often asymptomatic in immunocompetent people but can be dangerous in pregnant women on first contact, as diaplacental transmission to the foetus can lead to severe damage (Baneth et al. 2016). Human toxocariasis is caused by migration of Toxocara spp. larvae into different parts of the body (visceral larva migrans, ocular larva migrans and neural larva migrans) (Strube et al. 2020). Seroprevalence is high in the human population (Strube et al. 2020), but serologic tests do not routinely differentiate between T. canis and T. cati (Jimenez Castro and Sapp 2020). The significance of T. cati in toxocariasis is therefore unclear, but confirmed cases have been described in the literature (Jimenez Castro and Sapp 2020). An important risk of infection are environments contaminated with Toxocara eggs through faeces (e.g. gardens, playgrounds, parks) (Kutzer and Greil 2000). Giardia duodenalis is a common parasite in cats. Cats usually harbor the cat-specific genotype F, but zoonotic genotypes/subtypes can also occur (Feng and Xiao 2011; Pallant et al. 2015). Nevertheless, the risk of infection from cats appears to be low in Germany. Human giardiasis is a travel-associated disease. In 2022, 44% of the 1,780 reported cases in Germany were acquired abroad (Robert Koch-Institut 2024) and in a study the contact with animals was not associated as risk factor for symptomatic disease in Germany (Espelage et al. 2010). As cats are significantly less susceptible to infection with E. multilocularis than dogs, they play a less important role in transmission to humans (Baneth et al. 2016). In rarer cases, infection with D. caninum in humans occurs through the unintentional ingestion of an infected intermediate host such as fleas (Rousseau et al. 2022).

In Germany 83.3% of cats are dewormed less frequently than recommended by the ESCCAP (European Scientific Counsel Companion Animal Parasites) depending on the risk groups and cat owners deworm their pets significantly less frequently than dog owners (Strube et al. 2019). In addition, free-roaming cats pollute the environment with their faeces more frequently than dogs, whose owners usually collect and dispose of their droppings. This increases the risk of infection of cats and the risk of zoonosis for humans. Regular examinations of faeces for parasites and consequent treatment of positive animals are important to minimize contamination of the environment. Surveys help to identify changes in the occurrence of endoparasites in the cat population in Germany, which helps veterinarians to better educate owners and implement appropriate parasite management.

This study aimed to investigate the frequency of endoparasites in faecal samples from cats submitted to a commercial veterinary laboratory in Germany.

Materials and methods

Faecal samples

Faecal samples from cats tested for endoparasites at a commercial veterinary laboratory (Laboklin GmbH & Co. KG, Bad Kissingen, Germany) between January and December 2019 were retrospectively evaluated. The samples were sent in by veterinarians and animal owners from all federal states in Germany (Bavaria n = 1,576; Baden-Württemberg n = 1,524; North Rhine-Westphalia n = 1,494; Lower Saxony n = 931; Hesse n = 881; Rhineland-Palatinate n = 753; Schleswig–Holstein n = 290; Berlin n = 238; Brandenburg n = 231; Thuringia n = 161; Saxony-Anhalt n = 147; Mecklenburg-Western Pomerania n = 117; Saxony n = 101; Saarland n = 100; Hamburg n = 79; Bremen n = 45) due to clinical symptoms, therapy controls and routine examinations of healthy animals.

Faecal examinations

Of the 8,668 samples, 5,571 were tested with one and 3,097 with more than one diagnostic test, depending on the customer's request. Samples included in this study (Table 1) were tested by microscopic examination with the flotation method as well as the sodium acetate-acetic acid-formalin concentration (SAFC) technique (n = 6,425), microscopic examination with the Baermann-Wetzel migration technique (n = 721), coproantigen enzyme-linked-immunosorbent assay (ELISA) for G. duodenalis (n = 3,233) and Cryptosporidium spp. (n = 346) or polymerase chain reaction (PCR) for G. duodenalis (n = 1,007) and Cryptosporidium spp. (n = 672). The kind of diagnostic test was either requested as a single service or included in one of several different diagnostic panels. Samples for which the background information did not include patient age were excluded from the analysis, except for the analysis of the Baermann-Wetzel migration technique for lungworms due to the low number of positive samples. The samples arrived via overnight transport in the laboratory and were analysed in the laboratory on the same day they arrived. Samples that arrived on a Saturday were stored at 5 °C until Monday.

Tab 1.

Number of faecal samples per test performed and age distribution of the samples analysed

Age groups Number of examined samples (n) per test
Flotation method and SAFC technique Baermann-Wetzel migration technique Giardia duodenalis (ELISA and PCR) Cryptosporidium spp. (ELISA and PCR)
 ≤ 3 months 498 N/A 420 92
 > 3–6 months 629 N/A 511 132
 ≥ 6–12 months 601 N/A 475 123
 ≥ 1–5 years 1,712 N/A 1,199 278
 ≥ 5–10 years 1,193 N/A 686 164
 ≥ 10 years 1,792 N/A 949 229
Total 6,425 721

4,240

(ELISA: 3,233; PCR: 1,007)

1,018

(ELISA: 346; PCR: 672)
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SAFC sodium acetate-acetic acid-formalin concentration, N/A not available

Microscopic examination

The flotation method was done with a salt-glucose solution (specific gravity 1.3) and 1-5 g faeces were used. The suspension was left to stand for 10 min to allow the parasite stages to accumulate on the surface. The SAFC technique was performed with the Mini Parasep® SF faecal parasite concentrator according to the manufacturer’s instructions with Sodium Acetate-Acetic Acid Formalin Solution (SAF) Fixative, Triton X-100 Solution and ethyl acetate (Apacor Ltd., Wokingham, United Kingdom). The excretion of oocysts/cysts/eggs was determined semi-quantitatively and divided into low amount (1—10 eggs/oocysts/cysts per cover slip), medium amount (11—25 eggs/oocysts/cysts per cover slip) and a high amount (more than 25 eggs/oocysts/cysts per cover slip).

Detection of lungworm larvae was carried out using the Baermann-Wetzel migration technique, where the larvae migrate out of the faeces overnight (Deplazes et al. 2013). For the examination 5-15 g faeces were used. The test was not included in any diagnostic panel and therefore had to be ordered separately by customers. The lungworm larvae were not routinely differentiated in cats, as it was considered at the time that only A. abstrusus occurs in cats in Germany.

ELISA and PCR

Giardia coproantigen ELISA was performed with RIDASCREEN® Giardia (R-Biopharm AG, Darmstadt, Germany) and Cryptosporidium coproantigen ELISA with RIDASCREEN® Cryptosporidium (R-Biopharm AG, Darmstadt, Germany) according to the manufacturer’s instructions. For the tests 50–100 mg faeces were used.

For PCR tests 25 mg faecal samples were placed in 1000 µl “S.T.A.R. Buffer” (Roche Diagnostics GmbH, Mannheim, Germany) and mechanical disruption was performed in “MagNA Lyser Green Bead” tubes at 6500 rpm for 40 s in a MagNa Lyser (Roche Diagnostics GmbH, Mannheim, Germany). After short centrifugation, 200 µl of the supernatant were used for automated nucleic acid extraction via a commercially available kit (MagNA Pure 96 DNA and Viral NA Small Volume Kit, Roche Diagnostics GmbH, Mannheim, Germany) according to the manufacturer’s instructions. Real-time PCR was conducted to detect the small subunit ribosomal RNA gene of G. duodenalis (Verweij et al. 2003) and conventional PCR with subsequent gel electrophoresis was used to detect the 18S ribosomal RNA gene of Cryptosporidium spp. (Richter et al. 2011). In case of a positive result in the latter PCR the presence of Cryptosporidium spp. was verified via Sanger sequencing and subsequent comparison of the retrieved sequences via Basic Local Alignment Search Tool (BLAST). Each PCR run included a negative and a positive control, as well as an extraction control in each sample, to check for nucleic acid extraction and PCR inhibition (DNA Process Control Detection Kit, Roche Diagnostics GmbH, Mannheim, Germany).

Age distribution

Faecal samples examined microscopically by flotation method and SAFC technique were divided into six age groups in order to assess the correlation between age and infection rate (n = 6,425; Table 1). Parasites, which were detected in less than 50 samples, were excluded from the analysis (Ancylostomatidae, Taeniidae, T. gondii/H. hammondi, Capillaria spp., T. leonina, Sarcocystis spp., D. caninum), as well as lungworms since the flotation method and the SAFC technique are not the gold standard method for lungworm detection. Results of ELISA and PCR testing for G. duodenalis were combined and analysed according to six age groups (n = 4,240; Table 1). Results of ELISA and PCR testing for Cryptosporidium spp. were similarly combined and analysed in two age groups only (< 1 year n = 347; ≥ 1 year n = 671) due to a low total number of positive samples.

Statistical methods

PSPP (version GNU pspp 1.6.2) was used to perform Pearson's chi-square test (significance at p < 0.05). Where expected cell counts were < 5, Fisher’s exact test was applied. Yates’ correction was used in one degree of freedom.

Results

Microscopic examination by flotation method and SAFC technique

Endoparasites were detected in 8.5% (< 1 year: 16.7%; > 1 year: 5.4%) of the feline faecal samples examined (n = 6,425 [1,728 < 1 year; 4,697 > 1 year]). In 7.6% of the samples one type of parasite could be found, while coinfections could be detected in 0.9% of faecal samples, including 0.8% with two and 0.1% with more than two different parasites. The detected parasites were mainly nematodes (49.5%) and protozoa (47.7%), while cestodes (2.8%) were rarely detected with the applied methods (n = 606). The most frequently detected parasite stage in the microscopic examination were eggs from T. cati (3.8%; < 1 year: 7.3%; > 1 year: 2.5%), followed by Cystoisospora spp. oocysts (2.3%; < 1 year: 5.6%; > 1 year: 1.1%) and G. duodenalis cysts (1.9%; < 1 year: 3.8%; > 1 year: 1.3%). Less frequently detected parasites stages were Ancylostomatidae eggs (0.3%), lungworm larvae (0.3%), T. gondii/H. hammondi oocysts (0.2%), Taeniidae eggs (0.2%), and Capillaria spp. eggs (0.2%). T. leonina eggs (0.08%), Sarcocystis spp. sporocysts (0.06%) and D. caninum eggs (0.02%) were found only sporadically in faecal samples (Fig. 1). Eggs of Taenia spp. and Echinococcus spp. (grouped in family Taeniidae), as well as oocysts of T. gondii and H. hammondi cannot be distinguished morphologically.

Fig. 1.

Fig. 1

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Detection rate of parasite stages in faecal samples of cats (n = 6,425) detected by flotation method and SAFC technique

In 544 positive faecal samples a total of 606 parasites could be detected. Of the total detected parasite infections (n = 606), the oocyst/cyst/egg excretion was low in 60.4%, moderate in 14.0% and high in 25.6%. In faecal samples with roundworms (T. cati and T. leonina; n = 248), 59% had a low, 15% a moderate, and 26% a high amount of eggs. Of the samples in which Cystoisospora spp. were detected (n = 146), 60% had a low amount of oocysts, 14% had a moderate amount, and 25% had a high amount. More than half (52%) of the samples with G. duodenalis (n = 124) had a low amount of cysts, while 15% had a moderate and 33% had a high amount of cysts. The majority (94%) of samples with Ancylostomatidae detected (n = 17) had a low amount of eggs present, with the remainder (6%) showing a moderate amount of eggs. Among samples in which Taeniidae were detected (n = 16), 75% showed a low amount of eggs, 19% a moderate amount, and 6% a high amount. All samples with Capillaria spp. (n = 15) detected had a low amount of eggs present. Samples with T. gondii/H. hammondi (n = 15) showed a low amount of oocyst excretion in 27%, a moderate in 13% and a high in 60% (Fig. 2).

Fig. 2.

Fig. 2

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Amount of oocyst/cyst/egg excretion in faecal sample for the parasites detected: T. cati and T. leonina (n = 248), Cystoisospora spp. (n = 146), G. duodenalis (n = 124), Ancylostomatidae (n = 17), Taeniidae (n = 16), T. gondii/H. hammondi (n = 15) and Capillaria spp. (n = 15). Low amount (1—10 eggs/oocysts/cysts per cover slip), medium amount (11—25 eggs/oocysts/cysts per cover slip) and high amount (more than 25 eggs/oocysts/cysts per cover slip)

Microscopic examination for lungworm larvae by Baermann-Wetzel migration technique

Lungworm larvae were found in 4.7% of samples (n = 721), with low amounts of larvae in 71%, moderate amount in 9% and high amount in 21% of positive samples (n = 34).

Detection of Giardia duodenalis and Cryptosporidium spp. coproantigen (ELISA) and DNA (PCR)

Giardia duodenalis coproantigen was detected in 8.1% of the 3,233 samples tested. Giardia duodenalis DNA was detected in 7.9% of 1,007 samples examined. Cryptosporidium coproantigen was detected in 1.7% of the 346 samples analysed. Cryptosporidium spp. DNA was detected in 2.5% of the 672 samples tested.

Comparison of different detection methods for Giardia duodenalis

The detection methods for G. duodenalis requested by customers varied. A comparative analysis of the results given by microscopic examination (flotation method and SAFC technique) and ELISA (n = 2,187) as well as microscopic examination and PCR (n = 254) can be seen in Table 2. Due to a small amount of samples, ELISA and PCR could not be compared.

Tab 2.

Comparison of microscopic examination (flotation method and SAFC technique), ELISA and PCR for the detection of G. duodenalis in faecal samples (microscopic and ELISA n = 2,187; microscopic and PCR n = 254)

ELISA PCR
positive negative positive negative
Microscopic
  positive 47 (2.1%) 9 (0.4%) 6 (2.4%) 0 (0.0%)
  negative 122 (5.6%) 2,009 (91.9%) 17 (6.7%) 231 (90.9%)
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Age distribution

A comparison of the six age groups showed a significant difference in the presence of parasites examined microscopically using the flotation method and the SAFC technique (p < 0.001). Cats in the first year of life (≤ 3 months: 20.7%, > 3 months—6 months: 16.9%, ≥ 6 months—12 months: 13.3%) were more likely to be infected than older animals (≥ 1 year—5 years: 8.1%, ≥ 5 years—10 years: 3.9%, ≥ 10 years: 3.9%) (Fig. 3). The detection rate decreases steadily from cats aged ≤ 3 months to cats aged ≥ 5—10 years. There was also a significant difference (p < 0.001) between the six age groups for each individual parasite species (Cystoisospora spp., G. duodenalis and T. cati), with the detection rate for each parasite being significantly higher in animals under 1 year of age (p < 0.001). In animals younger than 1 year, Cystoisospora spp. were detected significantly more frequently in cats ≤ 3 months (10.8%) than in the other age groups (p < 0.001); the parasite prevalence decreased continuously with age (Fig. 4). There was a trend of higher detection rates of T. cati in the age group ≤ 3 months as well as a continuous decrease in the detection rate with age was observed, though this did not reach significance in the comparison of the three age groups in the first year of life (p = 0.196). Conversely, there was a trend of higher detection rates of G. duodenalis cysts in the age groups > 3 months—6 months and ≥ 6 months—12 months than in younger kittens (≤ 3 months). Nevertheless, there was also no significant difference between the three age groups in the first year of life (p = 0.165).

Fig. 3.

Fig. 3

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Detection rate of parasites in different age groups by microscopical examination with flotation method and SAFC technique (≤ 3 months: n = 498; > 3 months – 6 months: n = 629; ≥ 6 months – 12 months: n = 601; ≥ 1 year – 5 years: n = 1,712; ≥ 5 years – 10 years: n = 1,193 and ≥ 10 years: n = 1,792)

Fig. 4.

Fig. 4

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Detection rate of specific parasites (Cystoisospora spp., T. cati, G. duodenalis) in different age groups by microscopical examination with flotation method and SAFC technique (≤ 3 months: n = 498; > 3 months – 6 months: n = 629; ≥ 6 months – 12 months: n = 601; ≥ 1 year – 5 years: n = 1,712; ≥ 5 years – 10 years: n = 1,193 and ≥ 10 years: n = 1,792)

The combined results of ELISA and PCR for the detection of G. duodenalis (Fig. 5) and Cryptosporidium spp. also showed a significantly higher detection rate in the first year of life than in older cats (p < 0.001 and p = 0.003, respectively).

Fig. 5.

Fig. 5

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Detection of G. duodenalis in different age groups, results of ELISA and PCR combined (≤ 3 months: n = 420; > 3 months – 6 months: n = 511; ≥ 6 months – 12 months: n = 475; ≥ 1 year – 5 years: n = 1,199; ≥ 5 years – 10 years: n = 686 and ≥ 10 years: n = 949)

Discussion

In present study, a large sample pool was examined for the presence of endoparasites in the faeces of cats from all German federal states, which were sent to a diagnostic laboratory.

Occurrence of intestinal helminths and protozoa

In the microscopic examination by flotation method and SAFC technique 8.5% of the faecal samples were positive for endoparasites, which was slightly higher than in a previous study by the same laboratory (Elze et al. 2014; sampling period 2011, 6.8% positive) and similar to another study of a German laboratory (Raue et al. 2017; sampling period 2003–2012, 8.4% positive). The copromicroscopic detection rate for the various intestinal endoparasites was also comparable with the retrospective studies by Raue et al. (2017) and Vrhovec et al. (2022) with T. cati being the most common parasite microscopically, followed by Cystoisospora spp..

However, G. duodenalis was the most frequently detected parasite in this study, using ELISA or PCR as detection method. This is consistent with other studies utilising an ELISA test for G. duodenalis detection in cats (Barutzki and Schaper 2011; Vrhovec et al. 2022). This must be taken into account when comparing the detection rates of studies that have used different methods to detect the same parasites, as ELISA and PCR are more sensitive detection methods for G. duodenalis than microscopic examination (Cirak and Bauer 2004; Sommer et al. 2018; Symeonidou et al. 2020). Although a direct comparison of ELISA and PCR was not possible in the present study, both methods achieved a similar percentage of positive results.

In addition to the different methods used to detect a parasite, the composition of the study population also influences the detection rate in studies, e.g. the number of animals under 1 year of age, the living conditions such as outdoor, stray and foster cats, which makes a direct comparison with other studies more difficult. For example, a study population with a high number of animals younger than 1 year can lead to a higher detection rate of endoparasites such as Cystoisospora spp. and T. cati, as in the study by Barutzki and Schaper (2011) with 46.4% of the animals younger than 1 year compared to 26.9% in the present study. While endoparasite detection in stray and foster dogs in Germany (Becker et al. 2012) was comparable to routine diagnostic samples (Csokai et al. 2024), there is a major difference between the parasite burden reported for stray and foster cats (Becker et al. 2012) and the rates of routine diagnostic samples found in this study. Stray cats had a higher number of positive faecal samples and a much higher detection rate of Cystoisospora spp., A. tubaeforme, Capillaria spp., Taeniidae and especially T. cati (Becker et al. 2012). A Finnish study also showed a higher detection rate of Toxocara/Toxascaris in outdoor cats compared to indoor cats (Näreaho et al. 2012), a differentiation which was not possible for the data set, which is presented in our study, due to the lack of background information.

There is little information on Cryptosporidium infections in cats in Germany. Previous studies with routine diagnostic samples have reported oocyst detection in 4.5% of 22 faecal samples examined by carbol-fuchsin staining (Raue et al. 2017) and in 4.8% of 26,517 faecal samples examined by ELISA (Vrhovec et al. 2022). The present study detected lower rates of positive samples, with 1.7% of 346 samples tested positive by ELISA and 2.5% of 672 samples tested positive by PCR. In a study with 19 cats showing diarrhoea, one was positive (5.3%) by PCR (Sotiriadou et al. 2013). Another study with 100 cats from three animal shelters with known endemic endoparasite infections, 30% were positive for Cryptosporidium by ELISA and 1% by carbol-fuchsin staining of direct faecal smear (Cirak and Bauer 2004). The authors discussed the possibility of false positive results as a possible reason for the high ELISA detection rate (Cirak and Bauer 2004).

Occurrence of lungworms

The current detection rate of lungworm larvae using the Baermann-Wetzel migration method was slightly higher (4.7%) than in an earlier study (3.4%) performed in the same laboratory (Elze et al. 2014). Vrhovec et al. (2022) also found an increase in positive samples in routine diagnostics from 2.6% (2004–2006) to 6.5% (2015–2017), which would be consistent with the trend suggested in our data. It remains unclear whether an increase in diagnoses is more likely due to an increase in lungworm infections in cats or due to increased awareness among veterinarians and consequently more testing of cats with the Baermann-Wetzel migration method in cats with respiratory symptoms. To the authors’ knowledge, retrospective studies of laboratories on this topic have not reported the proportion of outdoor cats within their study groups, a data point which would be crucial for interpretation of the trend, as cats with outdoor access have a higher risk for lungworm infection (Elsheikha et al. 2019). Barutzki and Schaper (2011) retrospectively reported a rather low detection rate of 0.5% in routine samples, while 6.6% positive faecal samples were found in a prospective study of cats with respiratory symptoms (Barutzki and Schaper 2013). The literature suggests that A. abstrusus is the most common lungworm in cats in Europe (Giannelli et al. 2017) while Troglostrongylus brevior, whose natural reservoir are wild cats, has only been detected in domestic cats in Italy, Spain, Greece, Romania and Bulgaria, and one case reported in Poland (Giannelli et al. 2017; Szczepaniak et al. 2019; Brianti et al. 2021; Morelli et al. 2021). So far, no infection has been reported in a domestic cat in Germany. However, T. brevior was also not detected in wild cats in Germany in an older study (Krone et al. 2008), while in a recently published study the lungworm was now frequently detected in the wild cat population (Bisterfeld et al. 2022). Lungworm larvae were not routinely differentiated in this study during the examination period, as it was considered at the time that only A. abstrusus occurs in cats in Germany.

Age distribution

Cats under 1 year of age were significantly more often infected with endoparasites (Cystoisospora spp., T. cati, G. duodenalis) than older animals (> 1 year), which is consistent with previous studies (Barutzki and Schaper 2011; Becker et al. 2012).

In animals younger than 1 year, Cystoisospora spp. had the highest detection rate in the group ≤ 3 months, while there was no significant difference for T. cati and G. duodenalis between the three age groups (≤ 3 months, > 3—6 months, ≥ 6—12 months). Barutzki and Schaper (2011) showed a similar tendency with significantly higher detection rates in the age groups under 3 months and > 3 months—6 months for Cystoisospora spp., T. cati and G. duodenalis.

Limitations of the study

Although this study did include many samples, they were not necessarily representative of the entire feline population in Germany. The samples sent to the diagnostic laboratory are without anamnesis or indication of testing (e.g. gastrointestinal diseases, controls after parasite treatment or routine examinations) and the majority of the samples are most likely of well-kept or looked-after cats and are therefore pre-selected, comparable to other studies mentioned above (Barutzki and Schaper 2011; Raue et al. 2017; Vrhovec et al. 2022). The number of cats included in studies with or without clinical signs, number of animals under 1 year of age or with outdoor access have an impact on results of parasite detection (Becker et al. 2012; Näreaho et al. 2012; Barutzki and Schaper 2013).

In addition, parasites are shed intermittently, and although clients are advised to submit a faecal sample of three consecutive days for analysis, it can be assumed that single samples were also submitted, which reduces the sensitivity of the detection rate.

Furthermore, the sensitivity of detection methods can differ. The flotation method, SAFC or MIFC (merthiolate-iodine-formaldehyde concentration) technique are less sensitive for detecting G. duodenalis than ELISA and PCR (Cirak and Bauer 2004; Sommer et al. 2018; Symeonidou et al. 2020). In the present study, the customers sometimes ordered the microscopic examination for endoparasites (includes detection of Giardia cysts) and the testing by Giardia ELISA or PCR together. Our results showed that ELISA and PCR are more sensitive in detecting G. duodenalis. Nevertheless, negative ELISA or PCR results can also occur (Hinney et al. 2015; Uehlinger et al. 2017; Uiterwijk et al. 2018), as was shown for the ELISA in the present study. In the case of very low excretion, an inhomogeneous distribution in the faeces can lead to a false negative result of the ELISA or PCR (Symeonidou et al. 2020), as well as components in faeces can lead to DNA degradation or can inhibit the PCR (Symeonidou et al. 2020). PCR-primers that amplify the small-subunit (SSU) rRNA gene of G. duodenalis and were used in this study, are more sensitive than other target gene loci (β-giardin, glutamate dehydrogenase, triosephosphate isomerase, elongation factor 1-alpha) (Nantavisai et al. 2007). On the other hand, misinterpretation in the microscopic examination due to the small size of cysts with a similar appearance of yeasts and plant remnants could possibly lead to a false positive result in microscopic evaluation (Dryden et al. 2006).

The use of different flotation media for the flotation method further influences the scope of parasite detection under the microscope. Flotation media with higher specific gravity (≥ 1.3), which were used in the present study, enable the detection of eggs from Taeniidae and Capillaria spp..

In present study cestode stages were rarely found using the flotation method and SAFC technique, which doesn´t show the true infection rate in the examined cat population, because postmortem examinations have shown that the detection of cestode infections is strongly underrepresented by faecal examination (Martínez-Carrasco et al. 2007).

Macroscopic examination of faeces and the fur around the animal's anus can be helpful in detecting proglottids which are excreted by animals infected with cestodes like D. caninum.

Conclusion

Giardia duodenalis was detected most frequently in feline samples examined in this study (detected by ELISA or PCR), followed by T. cati and Cystoisospora spp. (detected by microscopy after enrichment methods). Especially for G. duodenalis, ELISA or PCR tests showed a higher detection rate compared to microscopic methods. Thus, there is a need for differentiated diagnostic approach with immunologic or molecular test methods for G. duodenalis control. Toxocara cati and G. duodenalis both have zoonotic potential. As it is not possible to collect and dispose of the faeces from free-roaming cats, there is a higher risk of contamination of areas where children spend time or play. Therefore, regular parasitological examination of faeces and subsequent endoparasitic treatment is important to prevent zoonotic diseases. Cats are more likely to become infected with parasites in the first year of life, so especially breeders and owners of kittens should be educated and cared for by veterinarians in endoparasite control. The trend towards an increased detection rate of lungworms should be investigated further in order to possibly include these examinations in routine examinations in the future.

Acknowledgements

We would like to thank Anna Sophia Müller for the linguistic revision of the manuscript.

Author’s contribution

E.M. provided the idea for the study, J.C. performed the statistical analyses, interpretation of the data and wrote the manuscript text, E.M., A.H. and M.G. reviewed the manuscript.

Funding

No Funding was received for conducting this study.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval

No approval by an ethics committee was required as parasitological examinations were part of routine diagnostic examination.

Clinical trial number

Not applicable.

Competing interests

Elisabeth Müller is the head of the veterinary laboratory Laboklin GmbH & Co. KG. Jacqueline Csokai, Michaela Gentil and Anton Heusinger are employees of Laboklin GmbH & Co. KG. The laboratory offers diagnostic services including parasitological examinations for various samples.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Data Availability Statement

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