• Parasites, Hosts and Diseases
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• v.61 no.1
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• pp.33-41
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• 2023

The discovery of new antimalarial drugs can be developed using asynchronized Plasmodium berghei malaria parasites in vivo in mice. Studies on a particular stage are also required to assess the effectiveness and mode of action of drugs. In this report, we used endoperoxide 6-(1,2,6,7-tetraoxaspiro [7.11] nonadec-4-yl) hexan-1-ol (N-251) as a model antimalarial compound on P. chabaudi parasites. We examined the antimalarial effect of N-251 against ring-stage- and trophozoite-stage-rich P. chabaudi parasites and asynchronized P. berghei parasites using the 4-day suppressive test. The ED₅₀ values were 27, 22, and 22 mg/kg, respectively, and the antimalarial activity of N-251 was verified in both rodent malaria parasites. To assess the stage-specific effect of N-251 in vivo, we evaluated the change of parasitemia and distribution of parasite stages using ring-stage- and trophozoite-stage-rich P. chabaudi parasites with one-day drug administration for one life cycle. We discovered that the parasitemias decreased after 13 and 9 hours post-treatment in the ring-stage- and trophozoite-stage-rich groups, respectively. Additionally, in the ring-stage-rich N-251 treated group, the ring-stage parasites hindered trophozoite parasite development. For the trophozoite-stage-rich N-251 treated group, the distribution of the trophozoite stage was maintained without a change in parasitemia until 9 hours. Because of these findings, it can be concluded that N-251 suppressed the trophozoite stage but not the ring stage. We report for the first time that N-251 specifically suppresses the trophozoite stage using P. chabaudi in mice. The results show that P. chabaudi is a reliable model for the characterization of stage-specific antimalarial effects.

• Korean Journal of Veterinary Research
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• v.37 no.4
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• pp.785-791
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• 1997

Theileria spp.의 생활환에 대해서는 여러종류의 책을 통해서 잘 소개되어 있다. 그중 Theileria spp.의 분열소체 즉, merozoite는 주로 숙주의 적혈구내에 존재하는데 진드기에 의해 흡혈되지 않으면 더이상 발육하지 못하고 생을 마감한다고 여겨 왔다. 그러나 적혈구내 merozoite가 임파구에 다시 들어가 schizont로 복귀하여 분열 증식된다는 가설은 아직까지 증명된 바 없다. 본 실험은 T sergenti merozoite의 schizont로의 복귀를 입증하고자 수행되었다. T sergenti에 감염되지 않은 3개월령의 송아지를 비장적출시킨 후 T sergenti merozoite에 감염된 순수적혈구를 인공감염시켰다. 인공감염후 경시적으로 혈액과 임파액을 채취하여 적혈구내 T sergenti 감염을 조사하고 백혈구 감별혈구를 계산하였으며 임파구내 schizont 출현을 관찰하여 다음과 같은 결과를 얻었다. 1. 혈구내원충 감염율(parasitemia : PE)은 인공감염후 28일째 최고치인 10.5%를 보였으며 그후 5%이내의 수준을 유지하다가 70일째 다시 8.5%의 상승점을 보였다. 2. 백혈구 감별혈구계산에서는 감염초기에는 호중구가 주종을 이루다가 감염후 19일을 기점으로 임파구(60~80%)가 급격히 증가하여 실험종료 때까지 유지되었다. 3. 인공감염후 19~23일, 59~63일 사이에 말초혈액내 임파구에서 분열 증식하고 있는 schizont를 관찰할 수 있었다. 4. 인공감염후 7일부터 림프액내 임파구의 크기가 커지면서 blast-formation이 진행되었으며 실험종료때까지 유지되었다. 이상의 결과로 보아 적혈구내 merozoite가 임파구에 다시 들어가 schizont로 복귀하여 분열 증식함을 입증하여 기존의 T sergenti 생활사는 수정되어야 된다고 사료된다.

• Korean Journal of Veterinary Research
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• v.36 no.2
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• pp.453-461
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• 1996

Eighteen holstein-calves(4~5 months old) in a divided groups including the matched control were immunized with $100{\mu}g/dose$ of 34kDa, 45kDa polypeptide and T sergenti merozoite vaccine(protein content $100{\mu}g/dose$) respectively, previously mixed with aluminium hydroxide to elicit antibodies. All groups of calves were boosted with same dose and intervals. The animals were challenged by tick infestations in the endemic pasture of theileriosis from March to September 1994. The animals were monitored for the erythrocyte count, parasitemia, hematocrit and the specific antibody reactions elicited by immunization. The immunological responses demonstrated that vaccination with 34kDa polypeptide and T sergenti merozoite derived vaccine inhibited to produce the 75kDa band immunological responds even in the vaccinated calves after being challenged by tick infestations in the pasture. However, the specific antibody reactions were detected at the 32kDa band in the nonimmunized calves and T sergenti merozoite derived vaccine by the western blot. The 34kDa polypeptide vaccine and T sergenti merozoite derived vaccine were evaluated to be able to protect inducing anemia and to decrease parasitemias level. These vaccines have the efficacy of inhibition to produce a certain antigen corresponding 75kDa band antigen of parasite in the calves as challenged with tick infestations.

• Parasites, Hosts and Diseases
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• v.55 no.3
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• pp.255-267
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• 2017

Malaria is an infectious disease affecting humans, which is transmitted by the bite of Anopheles mosquitoes harboring sporozoites of parasitic protozoans belonging to the genus Plasmodium. Despite past achievements to control the protozoan disease, malaria still remains a significant health threat up to now. In this study, we cloned and characterized the full-unit Plasmodium yoelii genes encoding merozoite surface protein 1 (MSP1), circumsporozoite protein (CSP), and Duffy-binding protein (DBP), each of which can be applied for investigations to obtain potent protective vaccines in the rodent malaria model, due to their specific expression patterns during the parasite life cycle. Recombinant fragments corresponding to the middle and C-terminal regions of PyMSP1 and PyCSP, respectively, displayed strong reactivity against P. yoelii-infected mice sera. Specific native antigens invoking strong humoral immune response during the primary and secondary infections of P. yoelii were also abundantly detected in experimental ICR mice. The low or negligible parasitemia observed in the secondary infected mice was likely to result from the neutralizing action of the protective antibodies. Identification of these antigenic proteins might provide the necessary information and means to characterize additional vaccine candidate antigens, selected solely on their ability to produce the protective antibodies.

• Korean Journal of Veterinary Research
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• v.42 no.2
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• pp.261-268
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• 2002

Bovine piroplasmosis caused by Theileria sergenti results in economic loss in the dairy industry. The majority of calves infected with T. sergenti in Korea harbor mixed populations with Buffeli, Chitose and Ikeda types. The T. sergenti types of the infected calves were examined to evaluate the effects of diminazene aceturate on their infection. To confirm the type of the T. sergenti infection, the allele-specific PCR was performed with the erythrocyte specimen from the 5 naturally infected calves. The dfferent allele-specific genes encoding the p32, p33 and 34, the immunodominant piroplasmin surface proteins, were amplified using the 3 sets of the oligonucleotide primers by PCR. The calves were treated with diminazene aceturate at the dose of 2mg/kg once intravenously and monitored for 12 months at one month intervals by the allele-specific PCR. Diminazene aceturate did not effect the Ikeda type infection. But diminazene aceturate effected the Chitose and Buffeli type infection reducing T. sergenti parasitemia. It is postulated that diminazene aceturate may effect the infection of the Chitose and Buffeli types, but not that of Ikeda type.

• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.465-471
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• 1990

The fine structure of the inoculated Theileria sergenti on the splenectomized Korean native cattle was observed to delineate the morphological. characteristics with transmission and scanning electron microscope. The cattle was inoculated with 1.5ml cryopreserved stabilate ($5.63{\times}10^6/{\mu}l$, PE 3%). At peak parasitemia (40%), infected blood was collected, washed and then T sergenti was observed. Scanning electron micrograph of the erythrocytes infected with T sergenti appeared various irregular from involving specific swelling, and abnormal projections like acantocyte, echinocyte and knizocyte. Transmission electron microscopic studies of T sergenti showed that piroplasm possess intracytoplasmic food vacuole, rhoptries and tubule. Merozoite, $0.6{\sim}1.81{\mu}m$ to $0.4{\sim}1.21{\mu}m$ in length, surrounded by 10~15nm thickness of pellicula. which is surrounded by a single unit membrane. Various size of veil which was observed in stroma of erythrocytes infected with T sergenti, located at the proximate part of the merozoite. The merozoite multiplied by means of binary fission so that two and more oval-like merozoites in the stroma of infected erythrocyte could be observed.

• Journal of Veterinary Clinics
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• v.33 no.1
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• pp.16-20
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• 2016

This study was performed to estimate the clinical use of combination therapy with atovaquone/proguanil and azithromycin as a effective treatment in dogs infected with Babesia gibsoni. Eight mixed-breed dogs that were infected naturally with B. gibsoni were used in this study. Four dogs (No. 1-4) as experimental group received atovaquone/proguanil and azithromycin therapy. As for the other four dogs as the control group (No. 5-8) were administered diminazene aceturate and tetracycline/clindamycin. All the dogs in this study showed mild to severe anemia and thrombocytopenia. After initiating the treatment B. gibsoni in blood smears disappeared. PCR analysis of the experimental group showed negative results during the observation period, but more than one dog from the control groups showed continuous positive results. Atovaquone/proguanil and azithromycin combination therapy can significantly lower the B. gibsoni parasitemia levels and the results suggested that this combination therapy should be a new protocol for an effective treatment in dogs infected with B. gibsoni.

• Korean Journal of Veterinary Research
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• v.30 no.2
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• pp.223-229
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• 1990

A splenectomized 5-month-old calf was inoculated with cryopreserved Theileria sergenti infected blood originated from naturally infected Korean native cattle in Chonbuk district. At peak parasitemia (40.1%), blood was collected, washed, lysed and then the T sergenti merozoite was isolated by differential centrifugation. Antigenic profile of isolated T sergenti organism was analized by SDS-PAGE and western blotting techniques. Coomassie blue stained SDS-PAGE gel revealed at least twelve protein bands of approximately 14Kd, 28Kd, 30Kd, 34Kd, 36Kd, 38Kd, 41Kd, 56Kd, 66Kd, 72Kd, 97Kd and 116Kd in the merozoite homogenate. In western blot, although T sergenti antigen recognized by specific anti-T sergenti antibodies demonstrated 28Kd, 30Kd, 38Kd, 56Kd, 58Kd, 66Kd, 97Kd and 116Kd proteins. False positive reactions were also observed in normal bovine serum with T sergenti and normal erythrocytic antigens. Therefore, predominant proteins of T sergenti merozoite antigen were found to be 28Kd, 30Kd, and 41Kd proteins of molecular weights. On going studies we will analyze the relative importance of those antigens for immunity of T sergenti in Korean native cattle.

• Parasites, Hosts and Diseases
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• v.60 no.4
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• pp.295-299
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• 2022

Malaria elimination and control require prompt and accurate diagnosis for treatment plan. Since microscopy and rapid diagnostic test (RDT) are not sensitive particularly for diagnosing low parasitemia, highly sensitive diagnostic tools are required for accurate treatment. Molecular diagnosis of malaria is commonly carried out by nested polymerase chain reaction (PCR) targeting 18S rRNA gene, while this technique involves long turnaround time and multiple steps leading to false positive results. To overcome these drawbacks, we compared highly sensitive cytochrome oxidase gene-based single-step multiplex reaction with 18S rRNA nested PCR. Cytochrome oxidase (cox) genes of P. falciparum (cox-III) and P. vivax (cox-I) were compared with 18S rRNA gene nested PCR and microscopy. Cox gene multiplex PCR was found to be highly specific and sensitive, enhancing the detection limit of mixed infections. Cox gene multiplex PCR showed a sensitivity of 100% and a specificity of 97%. This approach can be used as an alternative diagnostic method as it offers higher diagnostic performance and is amenable to high throughput scaling up for a larger sample size at low cost.

• Korean Journal of Veterinary Research
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• v.33 no.1
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• pp.101-108
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• 1993

To examine the effects of vaccination against Babesia gibsoni(B gibsoni) infection in dogs, 15 normal mixed-breed dogs(5 months to 1 year old) were divided into 3 groups with 5 dogs in each group. One of them was selected as control group(group A) and other were selected as experimental groups(group B and C). The group B was vaccinated with antigen which were mixed 0.2% of formalin treated B gibsoni and sonicated one. The group C was inoculated Theileria sergenti as a non-specific antigen. The results obtained in this experiment were summarized as follows; 1. After first vaccination, antibody titers of group B and C were increased 5 times(1:200) than those of control group(1 : 40). The antibody titers of group C were increased more than that of group B after second vaccination. When challenged with the living protozoa(Babesia gibsoni), the antibody titers of C group were elevated higher than that of B group and maintained steadly. Those were not exceeded over 1 : 5,000 for 4 weeks in all 3 groups. 2. After challenge, the peak time of the parasitemia appeared nearly on the 15th day(12~18 days) in all groups. During this period, the rate of parasitized erythrocytes in control group was $55.0{\pm}5.4$‰. But that of group B and C were $41.3{\pm}38.8$‰ and $15.2{\pm}16.3$‰, respectively. 3. After challenge with B gibsoni, all of the values of PCV, Hb, RBC and total leukocytes counts were decreased in both of the experimental and the control. 4. In all groups, there were increased lymphocytes and monocytes after challenge with the protozoa.