Sensitivity and specificity of various serological tests for the detection of Toxoplasma gondii infection in naturally infected sheep

doi:10.1016/j.vetpar.2008.02.016

Veterinary Parasitology

Volume 153, Issues 3–4, 31 May 2008, Pages 359-362

https://doi.org/10.1016/j.vetpar.2008.02.016 Get rights and content

Abstract

Comparative serological examination of 300 serum samples from sheep slaughtered in the main abattoir in Cairo, Egypt revealed a higher prevalence of toxoplasmosis (43.7%) with the modified agglutination test (MAT), followed by the enzyme linked immune-sorbant assay (ELISA) (41.7%) and the indirect fluorescent antibody test (IFAT) (37%), while the lowest prevalence was detected with the dye test (DT) (34%). When the data from the first three serological tests were compared with that of the DT test, which was used as a reference test for toxoplasmosis, MAT had the highest sensitivity (96%), followed by ELISA (90.1%) and IFAT, which demonstrated the lowest sensitivity (80.4%). Conversely, IFAT had the highest specificity (91.4%), followed by MAT (88.9%) and ELISA (85.9%).

Introduction

Toxoplasmosis is a parasitic disease that causes serious economic losses in the sheep industry all over the world, especially at the time of lambing (Blewett and Trees, 1987). Toxoplasma gondii infection is a common cause of abortion in pregnant women and female animals, and can cause blindness and mental retardation in children. In contrast, animal fetuses may be mummified, stillborn or may be born weak and die within weeks after birth. Immune-deficient individuals, particularly AIDS patients, suffer from fatal toxoplasmic encephalitis (Luft and Remington, 1992).

The use of different serological tests for T. gondii in sheep has been demonstrated in several countries. Using indirect fluorescent antibody test (IFAT), the prevalence of T. gondii was 55% in Swedish pregnant ewes (Uggla et al., 1983), and 33.3% in Australian lambs (Munday et al., 1987). Using enzyme linked immune-sorbant assay (ELISA), the prevalence of infection was 62.5% in the USA (Malik et al., 1990), while by modified agglutination test (MAT), the prevalence of infection was 64% in 4–6-year-old and 80% in ewes over 6 years of age in the USA (Dubey et al., 1986), and 13.9% and 28.5% in sheep kept under an intensive and extensive management system in Uruguay (Savio and Nieto, 1995). Using SFT, the prevalence of infection was 33.2% in 0–12-month-old sheep and 47% in sheep older than 1 year in Turkey (Aktas et al., 2000).

Many studies have investigated the incidence of T. gondii in Egyptian sheep, which was shown to be 26.4% using Sabin Feldman test (Rifaat et al., 1979), 12.1% using IFAT (Maronpot and Botros, 1972), and 47% and 50% using ELISA and IFAT, respectively (El-Ghaysh and Mansour, 1994).

The objective of the present work was to evaluate dye test (DT), IFAT, ELISA and MAT serological tests for the diagnosis of T. gondii infection in slaughtered Egyptian sheep.

Section snippets

Blood and sera collected from slaughtered sheep

A total of 300 serum samples from slaughtered sheep at the main abattoir of Cairo were obtained, labeled, and stored at −20 °C.

T. gondii strains

The local strain of T. gondii used for antigen preparation was isolated by feeding kittens with meat samples obtained from freshly slaughtered ewes at the Cairo abattoir, Egypt according to the procedure described by Dubey and Beattie (1988).

Serological tests used for detection of T. gondii antibodies

Detection of T. gondii antibodies in the collected sera was examined using the following tests.

Serological examination for the detection of T. gondii antibodies

Examination of the 300 serum samples from slaughtered sheep through DT, IFAT, ELISA, and MAT revealed that 102 (34%), 110 (37%), 125 (41.7%), and 131 (43.7%), respectively, had antibodies against T. gondii (Table 1).

Comparative studies of the different serological tests used for detection of T. gondii antibodies

Sensitivity and specificity calculations of the serological tests revealed that MAT had the highest sensitivity (96%), followed by ELISA (90.1%) and IFAT, which demonstrated the lowest sensitivity (80.4%). On the other hand, IFAT had the highest specificity (91.4%), followed by MAT

Discussion

The methylene Blue Dye Test used in the present study showed that 34% of the examined sheep sera were sero-positive for T. gondii at a titer ≥1/64; similar results (33.2%) were recorded by Aktas et al. (2000) in 0–1-year-old sheep in Turkey. However lower incidence rate (26.4%) was recorded by Rifaat et al. (1979), and higher incidence rate (47%) was recorded by Aktas et al. (2000) in sheep over 1 year of age in Turkey.

IFAT showed that 37% of the examined sheep sera were sero-positive for T.

Conclusion

The results of the present work demonstrate the benefits of using the more sensitive and somewhat specific MAT for the detection of T. gondii antibodies in sheep sera. In addition, the serological tests used depended on Ag prepared from locally isolated T. gondii, which were much cheaper when compared with the expensive patented kits used in the previous studies in Egypt.

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Short communicationSensitivity and specificity of various serological tests for the detection of Toxoplasma gondii infection in naturally infected sheep

Abstract

Introduction

Section snippets

Blood and sera collected from slaughtered sheep

T. gondii strains

Serological tests used for detection of T. gondii antibodies

Serological examination for the detection of T. gondii antibodies

Comparative studies of the different serological tests used for detection of T. gondii antibodies

Discussion

Conclusion

Brit. Vet. J.

Vet. Parasitol.

Vet. Parasitol.

Vet. Parasitol.

Sero prevalence of T. gondii in sheep in Malatya-Turkey

Saglik-Bilimleri-Dergisi

Direct agglutination test for diagnosis of toxoplasma infection: method for increasing sensitivity and specificity

J. Clin. Microbiol.

Toxoplasmosis of Animals and Man

Serological responses of equines feed T. gondii oocysts

Equine Vet. J.

Epizootiologic investigations on sheep farm with T. gondii-induced abortion

J. Am. Vet. Med. Assoc.

Sensitivity and specificity of various serological tests for detection of Toxoplasma gondii infection in naturally infected sows

Am. J. Vet. Res.

Detection of antibodies to Toxoplasma gondii in Egyptian sheep-herd using modern serological techniques

J. Egypt. Assoc. Immunol.

A micro modification of the Toxoplasma dye test

J. Parasitol.

Short communication
Sensitivity and specificity of various serological tests for the detection of Toxoplasma gondii infection in naturally infected sheep